EVALUATING THE SUSTAINABLE POTENTIAL OF BIOGAS

EVALUATING THE SUSTAINABLE

POTENTIAL OF BIOGAS GENERATION IN

SOUTH AFRICA

By

Gerhardus Paulus Jordaan

Thesis presented in partial fulfilment of the requirements for the degree of Master of Science

in Sustainable Agriculture at the University of Stellenbosch

Supervisor: Dr. E. Lötze Co-supervisor: Ms. E.M Vink

Dept. of Horticultural Science Dept. of Sociology and Social

University of Stellenbosch Anthropology

University of Stellenbosch

March 2018

i

DECLARATION

By submitting this thesis electronically, I declare that the entirety of the work contained

therein is my own, original work, that I am the authorship owner thereof and that I have not

previously in its entirety or in part submitted it for obtaining any qualification.

Date: March 2018

Copyright © 2018 Stellenbosch University

Stellenbosch University https://scholar.sun.ac.za

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ACKNOWLEDGEMENTS

I would like to take this opportunity to acknowledge the following people who have enabled

me to complete this thesis.

I am extremely grateful for the guidance of my supervisor Dr. E. Lötze, Ms. E.M. Vink as co-

supervisor and Ms. S. Horn for administrative support.

I would like to acknowledge NexusAG (Pty) Ltd for granting me a bursary to complete my

MSc Sustainable Agriculture degree, with special thanks to Mr. E.E. Cloete and Mr. J. Du

Preez.

I sincerely acknowledge the inputs, time and guidance of the following people who have been

major role players during this study: Mr. M. Tiepelt – Former chairman South African Biogas

Industry Association (SABIA), Mr. Y. Salie WISP facilitator at GreenCape, Mr. J. Lyons –

Green Economy Invest and Finance liaison at GreenCape and WESGROW, Prof. J. van

Rooyen - President of International Food and Agricbusiness Management Association

(IFAMA), Mr. P. Steyn – Managing Director Botala Energy Solutions, Mr. P. Atkins –

PACE Credible Carbon in Africa, Mr. R. Cloete – SELECTRA, Ms. M du Toit –

Architectural drafting.

I would like to acknowledge my friends and family for their continuous support.

Many thanks to my fellow MSc Sustainable Agriculture class mates; I wish you all the best.


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DEDICATION

I am grateful for this opportunity, to be able to dedicate this thesis to my beloved mother and

father, for their unconditional devotion, guidance, love and support.


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SUMMARY

With a global movement towards a more sustainable way of living, the two most noteworthy

hurdles to overcome in the quest for sustainable development are the unsustainable

management of waste and availability of clean energy. This study investigates the potential of

biogas generation in South Africa, referring specifically to its potential as a sustainable

agricultural practice and evaluates the process of anaerobic digestion and biogas utilisation as

a strategy to improve the country’s performance measured against two determinants of

sustainability, namely: 1) the provision of a clean and affordable energy supply and 2),

organic waste management.

A literature review was conducted to create a contextual framework against which biogas

generation potential can be evaluated. The status of the global biogas industry and how South

Africa compares to the world, not only in terms of the extent of the industry, but also in terms

of its sustainability performance as a country, is outlined.

The status, as well as the specific challenges and opportunities that are present in the South

African biogas industry, were further researched by means of face-to-face semi-structured

interviews with major role-players, among others representatives of the South African Biogas

Industry Association (SABIA) and GreenCape. This investigation indicated an interest in the

development of medium and commercial-scale biogas digesters which could be attributed to

opportunities that the biogas industry offer in terms of job creation, energy provision, carbon

mitigation, organic fertiliser production and waste management. The study confirmed that the

South African industry is currently faced with numerous challenges in terms of renewable

energy generation and supply, e.g. lack of government support, financial commitments

involved in its development, skills shortages, ethical challenges, limited water resources and

sustainable access to waste as a biomass source. However, innovative enablers do exist and

can promote the growth of the industry. These findings support the notion that biogas

generation can contribute significantly to sustainable development in South Africa.

By applying enabling factors such as streamlining EIA processes and licencing requirements

and creating a market for surplus energy generated, biogas generation can provide tax relief

through the anticipated implementation of carbon tax; create innovative solutions for waste

management and the organic fertiliser industry, while delivering ecosystem services such as


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carbon sequestration in soils and improved water and soil quality and ultimately, an increase

in food production. In addition, by integrating waste management and renewable energy

technologies, biogas generation could potentially contribute to the alleviation of poverty and

the well-being of society.

The rationale of the third part of the study was to establish the potential of farm-scale biogas

generation as a sustainable agricultural practice in South Africa. Findings are based on

interaction with two groups of farmers – 1) those without biogas digesters and 2), those with

biogas digesters. Purposive data collection was conducted through two self-administered

electronic surveys that were sent to farmers in both groups. The quantitative data obtained

was further supported and clarified through personal conversations with participants in both

surveys and measured against what is defined in this paper as sustainability: economic

potential, social potential and environmental potential – the three pillars of sustainability. For

this reason each of these categories were defined and the applicable factors that may impact

these categories, described.

The fourth part of the study aimed to identify the farm-scale biogas production system with

the most sustainable potential in an agricultural application that can benefit the pursuit of a

more sustainable future under local conditions. However, it was established that the

numerous variables in the South African biogas generation scenario complicate

implementation and that implementation should be site-specific to be feasible. A generic

model was developed to enable the evaluation of the sustainable potential of a specific

digester type at a specific site, taking all the variables into account. The model, a decision-

making tool, is based on the scoring of the three determinants of sustainability namely

environmental, social and economic according to a set of defining factors. Based on literature

and local expertise, collected through interviews, a comparison of the characteristics of

digester types with agricultural requirements enabled the identification of the Continuously

Stirred Tank Reactor (CSTR) digester as the type that could show the most potential when

implemented as a sustainable solution to address energy poverty, the rising costs of electricity

and waste management demands. The validation of the sustainable potential of the CSTR

digester type through further studies is recommended.

Although numerous existing challenges hinder the potential of biogas generation in South

Africa, the study concludes that biogas generation has potential to contribute to sustainable

agriculture and that it presents a substantial opportunity to promote sustainability and


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simultaneously address prominent challenges like waste removal, energy supply, water

recycling and skills development.


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OPSOMMING

In die wêreldwye strewe na ‘n meer volhoubare lewenswyse is daar twee struikeblokke van

belang – onvolhoubare afvalbestuur en die voorsiening van energie. Hierdie studie ondersoek

die potensiaal van biogasopwekking in Suid-Afrika, met spesifieke verwysing na die

potensiaal om as ‘n volhoubare landboupraktyk geïmplementeer te word en evalueer die

proses van anaerobiese vertering en biogasgebruik as ‘n strategie om die land se prestasie in

volhoubaarheid te verbeter, met spesifieke verwysig na 1) die voorsiening van skoon en

bekostigbare energie en 2), organiese afvalbestuur.

‘n Literatuurstudie is geloods as agtergrond waarteen die potensiaal van biogasopwekking ge-

evalueer kan word. Die status van die wêreldwye biogasindustrie en ook hoe Suid-Afrika

vergelyk met die res van die wêreld, nie net in terme van die omvang van die industrie nie,

maar ook in terme van sy volhoubaarheidprestasie, word bespreek.

Die status, sowel as die spesifieke uitdagings en geleenthede wat die biogasindustrie in Suid-

Afrika bied, is verder ondersoek aan die hand van aangesig-tot-aangesig semi-gestruktureerde

onderhoude met sleutelrolspelers in die industrie – onder wie verteenwoordigers van SABIA

(South African Biogas Industry Association) en GreenCape. Hierdie ondersoek het aangedui

dat die belangstelling wat heers in die ontwikkeling van medium tot groot (kommersiële)

biogas reaktors toegeskryf kan word aan die geleenthede wat dit bied in terme van

werkskepping, kragvoorsiening, koolstofmitigasie, produksie van organiese bemesting en

bestuur van afval. Die studie het bevind dat die Suid-Afrikaanse biogasindustrie deur

verskeie uitdagings in die gesig gestaar word, soos die opwekking en voorsiening van

hernubare energie, tekort aan regeringsteun, finansiële vereistes tydens ontwikkeling,

vaardigheidstekorte, etiese uitdagings, beperkte waterbronne en toegang tot afval as

voermeganisme, maar dat daar innoverende meganismes bestaan om die groei van die bedryf

te kan stimuleer. Dit bevestig die aanname dat biogasopwekking ‘n sleutelbydrae kan lewer

tot volhoubare ontwikkeling in Suid-Afrika. Deur hierdie innoverings toe te pas – soos die

vereenvoudiging van die omgewingsimpakproses en lisensiëringsvereistes asook die skep van

‘n afsetmark vir oortollige energie wat opgewek word – kan biogasproduksie

belastingsverligting meebring deur die verwagte implementering van koolstofbelasting, meer

doeltreffende afvalbestuur en die produksie van organiese bemesting terwyl ekostelseldienste

gelewer soos koolstofsekwestrasie in grond en verhoogde water- en grondkwaliteit wat


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uiteindelik kan lei tot ‘n verhoging in voedselproduksie. Hierbenewens kan biogasproduksie

ook moontlik bydra tot die verligting van armoede en die welsyn van gemeenskappe deur

afvalbestuur en die opwekking van hernubare energie te integreer.

Die mikpunt met die derde gedeelte van die studie was om die potensiaal van

biogasopwekking op plase as ‘n volhoubare landboupraktyk te evalueer. Bevindinge is

gebaseer op interaksie met twee groepe boere – 1) diegene wat nie biogasreaktors het nie en

2), diegene wat biogasreaktors het. Doelgerigte data is versamel met die hulp van

selftoegepaste opnames wat elektronies aan boere in albei groepe gestuur is. Inligting

ingewin is verder aangevul deur persoonlike gesprekke met deelnemers aan albei opnames en

gemeet teen dit wat in die artikel gedefineer word as volhoubaarheid, ekonomiese potensiaal,

sosiale potensiaal en omgewingspotensiaal – die drie bakens van volhoubaarheid. Ten einde

dit te kon doen, is elk van hierdie kategorieë gedefinieër en die faktore wat elkeen van hierdie

kategorieë bepaal, uiteengesit.

Die vierde gedeelte van die studie het ten doel gehad om die biogasreaktor met die meeste

potensiaal vir toegepassing in die landbousektor en wat dus Suid-Afrika se visie in terme van

‘n volhoubare toekoms kan bevoordeel, te identifiseer. Daar is egter vasgestel dat die groot

verskeidenheid veranderlikes in die Suid-Afrikaanse biogas scenario die implementering van

‘n enkele tipe biogasreaktor as ooglopende oplossing verhinder. Dit het aanleiding gegee tot

die ontwikkeling van ‘n generiese model wat as besluitnemingsmeganisme gebruik kan word

om die evaluering van die volhoubare potensiaal van spesifieke tipes biogasreaktors op ‘n

spesifieke terrein moontlik maak. Tweedens, gebaseer op literatuur as ook onderhoude met

kenners in die veld, is vergelykings getref tussen die eienskappe van bestaande

biogasreaktors en hoe dit antwoord in die vereistes van die landbousektor. Op grond daarvan

is die ‘Continuously Stirred Tank Reactor’ (CSTR) geïdentifiseer as die reaktortipe wat die

meeste potensiaal het om in die landbou geïmplementeer te word as volhoubare

landboupraktyk om die voorsiening van ‘n betroubare en bekostigbare bron van krag en en

sinvolle afvalbestuur moontlik te maak. Daar word dus voorgestel dat die volhoubare

potensiaal van die CSTR reaktor tipe gebruik word vir die evaluasie van die

geldigheid/validasie van die generiese model vir implementasie van hierdie biogasreaktor tipe

volgens die behoeftes van ‘n spesifieke terein.

Die gevolgtrekking was dat, selfs in die lig van die verskeie struikelblokke wat bestaan,

biogasopwekking in die Suid-Afrikaanse landbousektorvolhoubare potensiaal het, en ook

sodoende ‘n geleentheid bied op volhoubaarheid sowel as om prominente uitdagings aan te


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spreek soos afvalverwydering, enegie voorsiening, watersirkulering en die ontwikkelling van

vaardighede.


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EXPLANATION OF STYLE

This thesis is a compilation of chapters, starting with a literature review, followed by three

research papers. Each paper is prepared as a scientific paper for submission to South African

Journal for Plant and Soil. Selective repetition or duplication between papers is therefore

unavoidable.


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TABLE OF CONTENTS

Declaration i

Acknowledgements ii

Dedication iii

Summary iv

Opsomming vii

Explanation of style x

General Introduction 1

Literature review: OVERVIEW OF THE STATUS OF BIOGAS GENERATION, WITH

REFERENCE TO ITS SUSTAINABLE POTENTIAL IN SOUTH AFRICA 9

1.0 Introduction

1.1 Global biogas digester industry

1.2 Developing versus developed continents

1.2.1 European Union, with specific reference to Germany

1.2.2 Asia

1.2.3 Africa

1.2.4 North America

1.2.5 South America

2.0 Sustainability movements

2.1 Global sustainability movement

2.2 Sustainability in South Africa

2.3 How South Africa compares with the world

2.4 Biogas generation as a sustainable strategy to improve South Africa’s environmental

performance

2.4.1 Access to affordable and clean energy in South Africa

2.4.2 Waste management in South Africa


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3.0 Anaerobic digestion as sustainable strategy to meet energy demands and waste

management challenges

3.1 Feedstock importance and availability

3.2 Feedstock types in South Africa

3.2.1 Agricultural crop waste

3.2.2 Manure (poultry, cattle and dairy farms/feedlots)

3.2.3 Abattoir waste

3.2.4 Municipal solid waste

3.2.5 Sewage

3.3 Potential use of digestate as fertiliser

3.3.1 Effects and application of digestate

3.3.2 Digestate regulation processes in other countries

3.3.3 Potential in South African fertiliser industry

4.0 Literature cited

Paper 1: INVESTIGATING THE POTENTIAL OF BIOGAS GENERATION IN SOUTH

AFRICA AS A SUSTAINABLE PRACTICE, BY TAKING INTO ACCOUNT THE

STATUS, CHALLENGES AND OPPORTUNITIES OF THE LOCAL INDUSTRY 50

Paper 2: EVALUATING THE POTENTIAL OF ON-FARM BIOGAS GENERATION AS

A SUSTAINABLE AGRICULTURAL PRACTICE THROUGH INTERACTION WITH

THE FARMING COMMUNITY 91

Paper 3: DEVELOPING A DECISION-MAKING TOOL TO EVALUATE THE

SUSTAINABLE POTENTIAL OF ON-FARM BIOGAS DIGESTERS IN

SOUTH AFRICA 128

General conclusion 158

Appendices 161


1

GENERAL INTRODUCTION

Sustainability is an important concept in this study, as the potential of biogas utilisation is

evaluated against the principles of sustainability, namely economic, social and environmental

sustainability (DEA 2008, Nahman et al. 2009, Kuhlman and Farrington 2010, Morelli 2011,

GreenCape 2017b, Uwosh.edu 2017).Currently the world faces various challenges in terms of

sustainable living (UN 1987, UN 2015, UNDP 2017). With the global movement towards a

more sustainable way of life, the unsustainable management of waste and availability of clean

energy has been identified as significant hurdles that have to be overcome (UN 1987, UN

2015, SAGEN and SABIA 2016, CRSES 2017, UNDP 2017).

Even though South Africa has identified a vision and strategies to re-orientate its

development path to one that is more sustainable, the country fares extremely poorly in

comparison to other countries and is named as the worst performer out of the 21 countries in

sub-Saharan Africa (DEA 2008, Emerson et al. 2012, DEA 2013, EPI 2014, ESI 2017,

SEDAC 2017). South Africa’s sustainability policy imperatives are further driven by indices

such as the Environmental Sustainability Index (ESI) and Environmental Performance Index

(EPI) (EPI 2014, ESI 2017) and its signatory commitments to the Kyoto Protocol and the

Paris Agreement (NT 2014). Its poor environmental performance is, however, ascribed to the

way in which the country’s water shortages are managed, its contribution to air pollution and

climate change, as well as poor public health and agricultural practices.

Energy policies implemented in South Africa are required to address sustainability by

mitigating the effects of climate change, which simultaneously provides extra motivation for

the Department of Energy to include technologies such as gas, biomass, solar, thermal and

wind resources to meet South Africa’s future electricity needs (DoE 2016, DEA 2017). This

creates substantial opportunity for biogas generation, as biogas does what few other

renewable energy technologies do, which is to integrate waste management and energy

technology (Biogas 2013, Bachmann 2015, SAGEN and SABIA 2016, GreenCape 2017c).

This creates a promising pathway towards achieving sustainable development, by ultimately

reducing methane (CH4) and carbon dioxide (CO2), while incorporating the social dynamics

and requirements of a developing country by overcoming energy poverty, creating jobs,

supplying organic fertiliser, improving waste management, saving on energy and waste


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disposal costs and creating new business incentives (Smith 2011, Biogas 2013, NERSA 2013,

SAGEN and SABIA 2016, GreenCape 2017a, GreenCape 2017c, Tiepelt 2017).

Biogas generation may especially suitable as a sustainable agricultural solution to the

challenges faced by the developing world, and specifically the agricultural community in

South Africa, but the slow uptake of this technology both rurally and commercially compared

to other developed and developing countries, is attributed to numerous challenges (Smith

2011, Abbasi 2012, Amigun et al. 2012, Biogas 2013, Griffiths 2013, SAAEA 2016, SAGEN

and SABIA 2016, GreenCape 2016, GreenCape 2017a, GreenCape 2017c, Tiepelt 2017).

The first objective of this study was to evaluate the potential of the biogas digester industry

against the principles of sustainability, taking into account the status, challenges and

opportunities that the industry presents. For this purpose, face-to-face semi-structured

interviews (Babbie and Mouton 2001) were conducted with, among others, representatives of

the South African Biogas Industry Association and GreenCape, a non-profit organisation that

drives the widespread adoption of economically viable green economy solutions from the

Western Cape. Obtaining renewable energy through biogas generation proved to be

particularly complex and the South African industry is currently faced with numerous

challenges in terms of renewable energy generation and supply, due to a lack of government

support, financial commitments involved in its development, skills shortages, ethical

challenges, limited water resources and sustainable access to waste as a biomass source

(Terreblanche 2002, Smith 2011, AltGen, GIZ, SAGEN and GreenCape 2014, Ruffini 2014,

Torquati et al. 2014, GIZ-SAGEN 2015, Creamer 2016, GreenCape 2016, SAGEN and

SABIA 2016, GreenCape 2017a, GreenCape 2017b, GreenCape 2017c, Tiepelt 2017). These

findings created the opportunity to identify, investigate and recommend certain enabling

factors that can be pursued to further develop and promote the sustainable potential of the

industry. This includes streamlining legislation and licencing requirements, enabling the off-

take of energy generated through various means, providing adequate financial support

through grants and rebates, and creating opportunities for education and skills transfer

(AltGen, GIZ, SAGEN and GreenCape 2014, GIZ-SAGEN 2015, SAGEN and SABIA 2016,

GreenCape 2017c, Tiepelt 2017).

The second objective was to establish the potential of farm-scale biogas generation as a

sustainable agricultural practice in South Africa by investigating the reasons that may

contribute to the decisions of farmers either to invest in biogas digesters, or not to invest.


3

Self-administered electronic surveys (Babbie and Mouton 2001) were sent to the farmers for

data collection. The study analysed the understanding that farmers share about sustainability

and biogas generation; the effects of climate change on agricultural practices; the major

hindrances, challenges, opportunities and benefits facing biogas digesters in the agricultural

sector; the applicability of biogas digesters installed on farms and the reasons for either

implementation or no implementation of biogas digesters.

The third objective was to create a method by which the digester type applicable to farm-

scale digestion that could deliver the best results as a sustainable agricultural practice, can be

identified. However, the numerous variables in the South African scenario complicate

implementation and it is apparent that implementation locally should be site-specific to be

sustainably feasible (Lutge 2010, Biogas 2013, GreenCape 2017a, GreenCape 2017c,

Mutungwazi et al. 2017, Tiepelt 2017). A proposed generic model was developed as a

decision-making tool to enable the evaluation of the sustainable potential of a specific

digester type at a specific site, taking all the variables into account. Further, by considering

the characteristics of various agricultural digester models and comparing it to the needs of the

farming sector, a specific digester type was identified as having the most potential to be

implemented as a sustainable solution. This digester type was drafted and described as a

guideline for implementation at farm-scale.

In general, this thesis investigated the application of biogas generation in an agricultural

context. This was achieved by determining the country’s vision and commitment to

sustainable development and the opportunities that agricultural sector, together with biogas

generation, present. Its applicability in the agricultural sector was researched by consultation

with developers, development agencies and farmers. This information was used to propose a

decision-making tool (generic model) that will enable the evaluation of biogas digesters for

potential implementation on farm scale.


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23532009000500011&lng=en&nrm=iso>. ISSN 1996-7489.

NERSA (National Energy Regulator of South Africa) (2013). Media statement nersa registers

biogas production activities in rural areas in terms of the Gas Act, 2001 (ACT NO. 48 OF

2001). Published 28 October 2013. [Accessed on 20/09/2017] at

http://www.nersa.org.za/Admin/Document/Editor/file/News%20and%20Publications/Media

%20Releases%20Statements/Media%20statement%20-

%20NERSA%20registers%20biogas%20production%20activities%20in%20rural%20areas.p

df

Ruffini A. (2014) SA not using its biogas potential. ESI-Africa. [Accessed on 13/06/2017] at

https://www.esi-africa.com/sa-not-using-its-biogas-potential/

SAAEA (2016). South African Alternative Energy Association. Biogas digester for rural

households and small business. Article published: 4 August 2016. [Accessed on 28/03/2017]

at http://www.saaea.org/news/biogas-digester-for-rural-households-and-small-business

SEDAC (Socioeconomic data and application centre) (2017) Environmental Sustainability

Index. [Accessed on 17/05/2017] at http://sedac.ciesin.columbia.edu/

United Nations (UN). (2015) Millenium Development goals report 2015. [Accessed on

04/05/2017] at

http://www.un.org/millenniumgoals/2015_MDG_Report/pdf/MDG%202015%20rev%20%28

July%201%29.pdf

UNDP (United Nations Development Programme). (2017) What are sustainable development

goals? [Accessed on 19/06/2017] at http://www.undp.org/content/undp/en/home/sustainable-

development-goals/resources.html


https://www.greencape.co.za/assets/Uploads/GreenCape-Energy-Services-MIR-2017-electronic-FINAL-v1.pdf



http://www.saaea.org/news/biogas-digester-for-rural-households-and-small-business

http://sedac.ciesin.columbia.edu/

http://www.un.org/millenniumgoals/2015_MDG_Report/pdf/MDG%202015%20rev%20%28July%201%29.pdf


http://www.undp.org/content/undp/en/home/sustainable-development-goals/resources.html


8

Uwosh.edu. (2017) Definitions of sustainability. [Accessed on 20/06/2017] at

https://www.uwosh.edu/facstaff/barnhill/490-docs/readings/definitions.pdf

Presentations

AltGen, GIZ, SAGEN and GreenCape. (2014) An Estimation of the Job Potential and

Assessment of Skills Needs for the Biogas Industry in South Africa. Second Phase of

SAGEN’s programme: Market Development for Biogas Projects. Presentation.



9

LITERATURE REVIEW: OVERVIEW OF THE

STATUS OF BIOGAS GENERATION, WITH

REFERENCE TO ITS SUSTAINABLE POTENTIAL IN

SOUTH AFRICA

1.0 Introduction

Sustainability is an important concept in this study, as the potential of biogas utilisation is

evaluated against the principles of sustainability. With a global movement to a more

sustainable way of life, the two most noteworthy hurdles to overcome in the quest for

sustainable development are: 1) the unsustainable management of waste and 2) the

availability of clean energy (SAGEN and SABIA 2016, CRSES 2017). This review will refer

to South Africa’s demand for energy and waste management, and how these factors impact

on the sustainable potential of biogas utilisation.

Sustainability as a concept is discussed as defined in the National Framework for Sustainable

Development (NFSD) and the approach of the Department of Environmental Affairs (DEA),

including the Environmental Sustainability Index (ESI), The Environmental Performance

Index (EPI) and the strategy for sustainability in South Africa. The potential of biogas

utilisation could impact all three pillars of sustainability i.e. environmental, social and

economic, and for this reason it is found appropriate to define sustainability as applicable to

this study by referring to different definitions in literature (UN 1987, DEA 2008, Kuhlman et

al. 2010, Morelli 2011, EPI 2014, Uwosh.edu 2017).

In this review, sustainability is defined as: “The process of utilising and living within the

limits of available physical, natural and social resources in ways that promote social,

ecological and economic sustainability all at the same time, while allowing the living systems

in which humans are rooted to flourish in perpetuity” (UN 1987, Nahman 2009). The process

of biogas generation is seen as a promising pathway towards achieving sustainable

development, ultimately reducing methane (CH4) and carbon dioxide (CO2), while

incorporating the social dynamics and requirements of a developing country; promoting ways

to reduce energy costs, provide waste management solutions and produce organic fertiliser

for own use or as an additional source of income (Biogas 2013).


10

1.1 Global biogas digester industry

Internationally biogas has substantial potential as a renewable energy source. Regarded as the

so-called oxygen of an economy, energy is regarded as an undisputed driver of economic

development and has a key role in the socio-economic progress of countries (World

Economic Forum 2012). It is estimated that biogas could be a primary source of energy

covering up to 6% of the global energy supply, or a quarter of the present-day utilisation of

gas fossil CH4 (natural) gas (Holm-Nielsen et al. 2007).

Table 1: The estimated cumulative total number of biogas digester plants of all sizes and

types in the European Union, Asia and Africa.

Region Estimated total biogas

digester plants

Year Source

European Union 17 376 2015 EBA 2017

Asia 39 979 675 2012 Surendra et al. 2014

Africa 24 990 2012 Surendra et al. 2014

The global biogas plant market stood at 56 276 units in 2015 and expected to reach 59 697 by

the end of 2016 (Trancparencymarketreseach 2017). Table 1 indicates that Asia has the most

installed biogas digesters and that Africa and the EU are on a similar footing. The majority of

biogas digesters installed in Asia and Africa are however small-scale/domestic biogas

digesters, while the installations in the EU are on a larger/commercial scale (Zhu 2006, Smith

2011, Bond and Templeton 2011, Amigun et al. 2012). Surendra et al. (2014) estimated that

there were about 39.9 million biogas digesters in Asia in 2012. Therefore it can be accepted

that when referring to the estimated 2016 global total of 59 697, it refers to larger scale

biogas plants.

Europe is regarded as a leader in the field, with a total of 17 376 biogas plants and 459 bio-

methane plants active in the European Union in 2015 (EBA 2017) generating a total amount

of 60,6 TWh electricity which corresponds to the annual electricity usage of some 13,9

million European households (EBA 2017).

While Holm-Nielsen et al. 2007 estimated that biogas from wet organic matter (OM) such as

food waste, animal manure and crop by-products, could supply at least one quarter of all

future bioenergy, Abbasi (2012) predicted that by 2020 farms and large co-digestion biogas

plants that are part of farming and food-processing structures, will produce the largest volume

of biogas.


11

From these arguments it is clear that the technologies are available and ready for South

Africa to take advantage of. In addition to the availability of relevant technologies, there are a

number of incentives available locally and globally, such as carbon tax incentives (NT 2013),

which make farm-scale biogas plants a very attractive option for the agricultural sector

looking to reduce their carbon (C) footprint and save on electricity bills (Griffiths 2013,

Scharfy et al. 2017), also supported in findings of paper 1.

A study in 2012 by Barnhart compared three different types of biogas development scales in

Nepal, the United States and Sweden. It was found that in Nepal, biogas production mainly

supplies rural household energy, while in the United States biogas is produced on an

industrial-scale at waste management applications, with the generated energy being either

used on site or fed into a regional power grid (Barnhart 2012). In Sweden, biogas forms part

of a new energy strategy enabling municipalities to function energy independent and fossil

fuel free. These examples show how a renewable energy technology can be adapted and used

across scale and cultural/social contexts, in urban or rural environments and extending from

developing to developed countries (Barnhart 2012).

The global biogas market is likely to be further developed by increased support shown by

private bodies and the government to biogas plant owners, in terms of setting up of sufficient

regulations and financial incentives. The market is also being influenced by the constructive

contribution that fully functional biogas plants can make to reduce the volume of disposed

waste into landfills (Trancparencymarketreseach 2017). However, the growth rate could be

hindered by the lack of feasible waste segregation systems (Transparencymarketresearch

2017). This could restrict the availability of feedstock to biogas plants, discouraging several

new entrants into this competitive market (Biogas 2013).

It is expected that the biogas market will remain positive within the forecast period from

2016 to 2024 with a compound annual growth rate (CAGR) of 6,5%

(Trancparencymarketreseach 2017), providing a constant rate of return over this time

(Investopedia 2017). It is further predicted that this market’s volume will reach 86 964 biogas

plants at the end of 2022, which means that more than 30 000 units are expected to be

established within this period (Trancparencymarketreseach 2017).


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1.2 Developing versus developed continents

1.2.1 European Union, with specific reference to Germany

Internationally the use of biogas as an energy source is not new (Griffiths 2013). In recent

years, the impact of low-carbon, renewable bioenergy applications on a country’s national

energy sources have become increasingly important (Cherubini and Strømman, 2011).

In the European Union, the interest in bioenergy originates from the necessity to promote the

use of renewable energy sources to achieve objectives such as: (a) a reduction in dependence

on fossil fuels; (b) a reduction in emissions responsible for climate change; (c) the

development of new source of income for the agro-forestry sector; and (d) effective disposal

of wastes (Cherubini and Strømman, 2011).

Biogas in Europe is produced as so-called landfill gas during anaerobic degradation at

landfills, at large-scale industrial digesters used for sewage sludge, as well as in small-scale

digesters on individual farms (EU Handbook 2012).

According to the European Biogas Association’s statistical report (6th addition), the biogas

sector has been growing steadily with the number of biogas plants growing threefold in only

six successive years, with significant increases in the United Kingdom (with 77 additional

plants showing 17 % growth), Belgium (with 20 additional plants showing 11 % growth) and

the Netherlands (with 16 additional plants showing 6 % growth) (EBA 2017).

This is mainly due to new regulations that place restrictions on waste management and the

initiation of support schemes and financial incentives for renewable energy technology such

as government incentives for feed-in tariffs that have been implemented in many European

countries (EU Handbook 2012, GreenCape 2017a). In addition, farmers are encouraged by

the potential to earn additional income by planting energy crops and the opportunity to

produce electricity and/or heat from biogas while continuing with their traditional agricultural

activities (EU Handbook 2012, Torquati et al. 2014). These measures are aimed at increasing

renewable energy production, while enabling farm estates to reduce their energy dependence

and develop their income streams in the event of falling cereal, milk or meat prices (EU

Handbook 2012).

Waste water treatment works (WWTWs) are challenged with their requirement for optimal

energy usage and nutrient recycling (Bachman 2015). To meet such requirements, the

Netherlands has implemented an innovative concept, the NEW (nutrient, energy and water)

factory. The NEW factory concept suggests that wastewater should be regarded as a resource


13

of energy, nutrients and clean water rather a waste product. A roadmap has been set up on

how to achieve the goals of the NEW Factory by 2030 (Roeleveld et al. 2010).

Figure 1: Illustration of the amount of biogas plants in Europe per country in 2015.

(Source: EBA 2017).

Germany is one of the more prolific and successful implementers of biogas-power projects.

Almost 13 % of all renewable power generated in Germany can be attributed to medium to

large-scale biogas plants (Griffiths 2013). The German Biogas Association (GBA) estimated

that there were 7 320 electricity-producing biogas plants throughout Germany in 2011 and

predicted its growth to 7 874 in 2013 (GBA 2013). At the time it was estimated that Germany

was building a commercial digester roughly every eight hours. In 2011, the estimated

combined capacity of these plants was 2 997 MW, and in 2014 the estimated capacity

reached over 9 600 MW (GBA 2013, Ruffini 2014).

A significant factor contributing to the successful implementation of these projects is support

from the German government. The Renewable Energy Sources Act of 2000 guarantees

compensation for electricity produced by a renewable energy plant for 20 years (Griffiths

2013). A further reason for Germany’s success is its excellent infrastructure for producing as

well as distributing and using biogas. A sophisticated road and rail network allows effective

and reliable feedstock deliveries to biogas installations, and a well-established bio-waste

segregation and collecting system enables the further development of the substantial bio-

waste potential. A dense and country-wide electricity grid of approximately 1,7 million km in


14

length is available for electricity feed-in. Further extensions of this grid capacity are planned

for the short term as some remote areas have limited capacities for additional electricity feed-

in. A natural gas grid of more than 443 000 km is also available for bio-methane feed-in (EU

Handbook 2012).

Furthermore the German government announced an excellent support scheme with fixed

feed-in tariffs for different feedstocks, guaranteed access to the well-regulated grid and long-

term payment options. The feed-in law is regularly revised to keep the tariffs market-related

(EU Handbook 2012).

1.2.2 Asia

The Chinese have been using biogas from agricultural and household waste for cooking since

1929 (Chen et al. 2012). The last 30 years have seen the introduction of biogas to power

plants supplying from 20 kW up to 600 kW. Large agricultural biogas plants are a more

recent trend with only 3 % of the biogas plants installed used for power generation. Notable

biogas-to-power plants include a plant in Shandong province which utilises 500 tonnes of

chicken manure to generate 60 000 kWh of power daily, one in Meng Niu which treats

manure from dairy cows to generate 18 000 kWh per day and a project in Beijing which

digests manure and generates 38 000 kWh power per day (Chen et al. 2012).

Table 2: The amount of biogas plants fitted in Asia according to Ghimire 2013 and

Surendra et al. 2014.

Country

Year of initiation Total number of

plants fitted until

2009 (Ghimire 2013)

Total number of

plants fitted until

2012 (Surendra

et al. 2014)

China 1974 27 000 000 35 000 000

India 1970s 4 000 000 4 500 000

Nepal 1992 205 762 268 464

Vietnam 2003 75 820 152 349

Bangladesh 2006 10 019 26 311

Cambodia 2006 6 402 19 173

Laos PDR 2006 1 020 2 888

Indonesia 2009 50 7 835

Pakistan 2009 100 2 324

Bhutan 2011 - 265

Total 31 299 173 39 979 675


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1.2.3 Africa

While not as common as in Europe and Asia, domestic biogas digesters have been installed in

South Africa and Kenya since the 1950s. The most widely used biogas model is that of small-

scale biogas digester using household and domestic animal waste. Most African countries

show a low level of technological development with South Africa regarded as more advanced

(Amigun et al. 2012).

Griffiths (2013) estimated that by the end of 2013 there were as few as 150 biogas digesters

in South Africa. According to Ruffini (2014), there were some 200 registered biogas

digesters in the country by the end of 2014. Mark Tiepelt, former chairman of the South

African Biogas Association (SABIA) however, stated at the South African International

Renewable Energy Conference (SAIREC) in 2015 that there are around 700 digesters in the

whole of South Africa and that approximately 40 % are at existing waste water treatment

works, 50 % are small-scale domestic/rural digesters, and only around 10 % are commercial

installations (SAIREC 2015). GreenCape (2017c) estimated that there are currently 500

digesters in South Africa (200 digesters at WWTW; 300 used for other purposes). These

numbers lag far behind other African countries based on the findings of Ghimere (2013) and

Surendra et al. (2014) as listed in the table 3, with Kenya (6 749), Ethiopia (5 011) and

Tanzania (4 980) leading the way.

Table 3: The amount of biogas plants fitted in selected African countries (excluding South

Africa) measured by two studies Ghimire 2013 and Surendra et al. 2014.

Country Year of initiation Total number of

plants fitted until

2009 (Ghimire 2013)

Total number of

plants fitted until

2012 (Surendra

et al. 2014)

Rwanda 2007 434 2 619

Ethiopia 2008 128 5 011

Tanzania 2008 3 4 980

Kenya 2009 106 6 749

Uganda 2009 40 3 083

Burkina Faso 2009 1 2 013

Cameroon 2009 23 159

Benin 2010 - 42

Senegal 2010 - 334

Total 735 24 990

Studies have also shown that in sub-Saharan Africa half a billion people do not have access to

electricity in their homes. These households rely on biomass such as wood, animal waste and

agricultural residues to meet their basic needs for lighting, heating and cooking (Brown 2006,


16

Amigun et al. 2012, Msibi 2015). Parawira (2009) confirmed that these types of biomass

account for approximately 74 % of total energy usage in sub-Saharan Africa compared to the

25 % in Latin America and 37 % in Asia. There are however disadvantages to using these

fuels as the current rate of extracting these fuels is not regarded as sustainable. Moreover,

these fuels are not efficient energy carriers, their heat release is hard to control, and the

harmful gases released pose health risks (Amigun et al. 2012).

1.2.4 North America

It is estimated that there are more than 2 100 biogas systems that are operational in the United

States, with the potential for more than 11 000 new systems to be built (USDA 2014, ABC

2016). American Biogas Council (ABC) stated that 171 of these digesters (producing 100

MW) are on agricultural land, 1 500 are located at treatment plants for wastewater (where

only 250 digesters use the biogas produced) and 563 are located at landfills (ABC 2016).

Furthermore, the biogas production potential of the United States is estimated at 654 billion

cubic feet/year. If fully realised, these systems could yield sufficient energy to power about

three million American households and decrease methane emissions equal to 40 to 54 million

tonnes of greenhouse gas emissions by 2030 (USDA 2014).

1.2.5 South America

Currently, Brazil has 127 biogas plants, which are operating mainly with animal and

municipal waste; it is however estimated that about 100 million m³ methane could be

produced every day from waste water, municipal waste, agricultural waste and animal waste

in Brazil (Energy-decentral 2017).

By comparison, the total consumption of natural gas in Brazil reached 108 million m³ per day

in 2013. Given this potential, biogas utilisation has not yet taken off and despite the huge

potential of generating energy from crop residues/by-products and animal manure/slurry, up

to 50 % are currently still considered as mere waste, and as an environmental problem. It was

found that this is a result of lack of knowledge and limited access to appropriate technologies

(Energy-decentral 2017).

In other South American countries such as the rural areas of tropical regions like Costa Rica

and Colombia, and the hilly parts of Peru and Bolivia, biogas plants have been in use since

the 1980s (Pérez et al. 2014). These countries make use of the same simple constructions

such as used in Asia with small-scale domestic digesters containing a volume of 2-10 m3.


17

2.0 Sustainability movements

2.1 Global sustainability movement

The world currently faces various challenges in terms of sustainable living. This is supported

by the United Nations Development Programme’s statement that it is imperative today to

foster sustainable development (UNDP 2017). To this end the UNDP developed the

Sustainable Development Goals (SDGs), also known as the Global Goals (UNDP 2017). This

is a worldwide call to end poverty, safeguard the planet and make sure that all people flourish

and live in peace. These 17 SDGs build on the Millennium Development Goals, and include

among others current issues such as climatic change, achieving economic equality, and

promoting innovation, sustainable utilisation and peace and justice (UN 2015). These goals

are interconnected and work in partnership to achieve sustainable living for future

generations.

APPENDIX A: FIGURE OF 17 GLOBAL SUSTAINABLE DEVELOPMENT GOALS

(UNDP 2017)

APPENDIX A illustrates the 17 Sustainable Development Goals as stated by the UNDP

2017. Biogas utilisation has the potential to address ten of these goals, namely; no poverty

(goal 1), zero hunger (goal 2), good health and well-being (goal 3), affordable and clean

energy (goal 7), decent work and economic growth (goal 8), industry, innovation and

infrastructure (goal 9), sustainable cities and communities (goal 11), responsible consumption

and production (goal 12), climate action (goal 13) and life on land (goal 15).

With a current global population of 7.5 billion people (Worldometers.info 2017), it is

estimated that one billion people are still living in extreme poverty, with income inequality

worldwide continuing to increase (UN 2013). The impact of climate change threatens to

accelerate in the absence of sufficient safety measures and it is required to promote the

integrated and sustainable management of ecosystems and associated natural resources,

especially the global population forecasted to reach about 10 billion in 2056 (Carter and

Gulati 2014). This is projected at a current growth rate of 1.11 % (Worldometers.info 2017).

The United Nations stated that there is thus a need to take the necessary mitigating steps in an

effort to accomplish global sustainability (UN 2013).


18


In 2008, South Africa adopted the National Framework for Sustainable Development (NFSD)

described by the Department of Environmental Affairs (DEA) of which the purpose was to

outline the country’s vision for sustainable development and to specify strategic interventions

that are required to re-orientate South Africa’s development path to one that is more

sustainable (DEA 2008). According to this report, “South Africa aspires to be a sustainable,

economically prosperous and self-reliant nation that safeguards its democracy by meeting

the fundamental human needs of its people, by managing its limited ecological resources

responsibly for current and future generations, and by advancing efficient and effective

integrated planning and governance through national, regional and global collaboration”

(DEA 2008).

The 2008 report acknowledges the growing impact of economic growth and development on

environmental systems and natural resources (DEA 2008). In response, the NFSD commits

South Africa in the long-term to a programme of resource decoupling (DEA 2013).

Decoupling refers to the ability of an economy to grow without simultaneously escalating

environmental pressure. In 2011, the United Nations Environment Programme (UNEP)

warned that humanity could annually devour some 140 billion tonnes of biomass, fossil fuels

and minerals by 2050, unless nations can start decoupling economic growth from the rate of

natural resource consumption (UNEP 2011).

The NSFD also describes principles and trends in terms of sustainability in South Africa, and

suggests a set of actions that can be implemented through partnerships with civil society as

well as through cooperative governance practices (DEA 2013, DEA 2016).

The National Strategy for Sustainable Development and Action Plan (NSSD) elaborates on

the NFSD and other initiatives to address issues of sustainability by non-governmental

organisations (NGOs), academia, the business sector, government, civil society and other

important role players in South Africa. By recognising the need for new interventions to

promote sustainable development, the NSSD makes a valuable contribution towards

understanding and achieving sustainable development (DEA 2013, DEA 2016).

South Africa has adopted a systems approach to sustainability which is one where “…the

economic system, the socio-political system and the ecosystem are embedded within each

other, and then integrated through the governance system that holds all the other systems

together in a legitimate regulatory framework. Sustainability implies the continuous and


19

mutually compatible integration of these systems over time. Sustainable development means

making sure that these systems remain mutually compatible as the key development

challenges are met through specific actions and interventions to eradicate poverty and severe

inequalities” (DEA 2008, DEA 2013, DEA 2016).

2.3 How South Africa compares with the world

To compare South Africa’s overall progress towards environmental sustainability with other

countries ESI is used. The ESI measures complete progress and provides a complex

environmental profile of national environmental stewardship based on a collation of factors

resulting from a variety of datasets (SEDAC, 2017, ESI 2017). The ESI tracks 76 features of

environmental sustainability, including efforts towards environmental management,

contributions made to protect the global commons, natural resource endowments, pollution

levels (past and present), and the capacity of a society to perform better on the environmental

front (SEDAC 2017).

South Africa ranked 93rd out of 146 countries on the Environmental Sustainability Index in

2005 (DEA 2013). The score of 46.2 positions it below many of its southern African

Development Community (SADC) neighbours. Compared to New Partnership for Africa’s

Development (NEPAD) members, South Africa came 20th out of 40. Gabon, the Central

African Republic, Namibia, and Botswana took the first four places (DEA 2013). However,

after 2006, the ESI was replaced by the Environmental Performance Index (EPI) that placed

an even greater focus on environmental issues for which governments can be held responsible

(DEA 2013).

It is a harsh reality that out of the 132 nations that were evaluated, South Africa fared

extremely poorly at 128, with a low total score showing a worsening trend (Emerson et al.

2012, DEA 2013). The country is also named as the worst performer out of the 21 countries

located in sub-Saharan Africa, with Mozambique and Angola ranking at numbers 12 and 13.

South Africa’s ecosystem vitality (environmental management) ranked as poor and

deteriorating, while its environmental health (environmental impacts on human health) is

seen as poor but improving (DEA 2013).

This poor environmental performance is ascribed to the ways in which the country’s water

shortages are managed, its contribution to air pollution and climate change, poor public

health, as well as unstustainable mining and agricultural practices (OECD 2013). This re-


20

affirms the conclusions of the 2005 Environmental Sustainability Index that focused on South

Africa’s air and water quality, highlighting the country’s role in advancing climate change

and human vulnerability as particular problems (DEA 2008, DEA 2013, OECD 2013).

The DEA states that, in response, it is critical that government implements applicable

strategies and structures to overturn the situation in partnership with academia, community

organisations and business in order to take the steps that are required to reverse the numerous

identified negative trends (DEA 2013).

In 2014, South Africa showed improvement in its EPI done by Yale University where the

country moved up to an overall rank of 72 out of 178 countries (EPI 2014).

2.4 Biogas generation as a sustainable strategy to improve South Africa’s

environmental performance

Biogas does what few other renewable energy technologies do, which is to integrate waste

and energy technology (Biogas 2013). With the acknowledgement of the critical importance

of moving towards more sustainable development in South Africa (DEA 2013, DEA 2016),

the use of biogas digesters for electricity generation and efficient waste management could

play a defining role to improve and contribute to all three pillars of sustainability – i.e.

improving social dynamics (job creation, public health and living standards), promoting the

new business opportunities and protecting natural resources and environmental systems. The

National Framework for Sustainable Development (NFSD) indicates that such strategic

interventions are needed to re-direct South Africa’s development towards a more sustainable

path (UN 1987, DEA 2008, DEA 2013).

The Department of Energy (DoE) is assigned with the task to ensure secure and sustainable

energy delivery needed for South Africa’s socio-economic development. The DoE’s National

Development Plan (NDP) stipulates that South Africa will have an energy sector that

promotes economic growth and development through sufficient investment in energy

infrastructure by 2030 (DoE 2016). It further foresees that at least 95 per cent of the South

African populace will have access to either grid or off-grid electricity (DoE 2016).

Energy policies implemented should also address sustainability by mitigating the effects of

climate change (DEA 2017) providing extra motivation for the Department of Energy to

include technologies such as gas, biomass, solar, thermal and wind resources to meet the

South Africa’s future electricity needs (DoE 2016, DEA 2017). The plan proposes the use of


21

renewable resources such as gas as feasible alternatives to coal, and suggests that by 2030

these alternatives will supply at least 20 000 MW of the additional 29 000 MW of electricity

needed (DoE 2015, DoE, 2016).

Decisions regarding the energy mix of South Africa’s electricity supply industry should also

take into account its potential environmental impact, and the South African government has

made several commitments relating to minimising the environmental impact thereof. These

include, for example, a 34 % reduction in greenhouse gas emissions by 2020 (Teljeur et al.

2016).

2.4.1 Access to affordable and clean energy in South Africa

One of the most significant human-derived obstacles to overcome in terms of sustainability

is the access and supply to affordable and clean energy – SDG goal 7 (SAGEN and SABIA

2016, UNDP 2017). The United Nations (UN 2013) predicts that the energy needs of

hundreds of millions of households worldwide are likely to remain unmet unless substantial

headway is made in guaranteeing access to modern energy sources. The World Wide Fund

for Nature’s (WWF) Food Energy Water (FEW) report specifies energy as a major force in

ensuring effectiveness and sustainability in the farming sector (Carter and Gulati 2014). With

the ever-present electricity crisis and the recurrent consequences thereof, unsustainable

production and associated consumption have brought about huge economic and social costs

to South Africa making the need for improvement and innovations in this sector critical

(Teljeur et al. 2016).

Teljeur et al. (2016) found that as electricity prices rose and the reserve margin dropped in

the 2000s, attention shifted to large-scale renewable energy projects that could increase

supply relatively quickly. In 2009, NERSA developed renewable energy feed-in tariffs,

replaced in 2011 by the Department of Energy (DoE) with a competitive bidding process for

renewable energy, the Renewable Energy Independent Power Project Procurement

Programme (REIPPPP), consisting of mostly solar and wind power generation technology

(DoE 2015, DoE 2016, GreenCape 2017c). Independent Power Producers (IPPs) were then

introduced into the electricity supply industry through the highly successful REIPPPP which,

towards the end of 2015, had attracted R192 billion in private investments in 92 projects,

contributing 6 327 MW of contracted capacity. The Department of Energy’s IPP unit is

currently expanding the competitive procurement programme to include cogeneration, coal

and gas-to-power generation projects (DoE 2016, Teljeur et al. 2016).


22

Since 2007 and until August 2015, South Africa was faced with an unprecedented supply

crunch in the electricity sector with Eskom (state-owned vertically-integrated electricity

company) being unable to meet peak electricity demands, leading to recurrent load

shedding/electricity power cuts (Teljeur et al. 2016). This situation was triggered by a

number of causes, including delays in the construction and commissioning of coal-fired

power stations (Medupi and Kusile); Eskom’s strained financial position; unplanned outages,

and poor maintenance of ageing electricity plants. The critical challenge for the power sector

is thus to restore security of electricity supply and ensure sufficient electricity is generated to

meet demand (Teljeur et al. 2016).

South Africa has a very specific electricity load profile. Peak energy demand hours are in the

early morning between 07h00 and 10h00 and in the evening between 18h00 and 20h00. This

is largely because the majority of South African households utilise electricity for cooking and

heating as opposed to gas which is used in many European countries and the United States

(Griffiths 2013). This means that our peak demand requirement does not match the period in

which peak solar radiation gives the highest generation for solar energy. Wind energy profiles

also do not fit in predictably with this demand profile. With that said, it is clear that a

potential gap for biogas electricity generation could develop to alleviate electricity demand in

peak hours. As long as a biogas plant is maintained and correctly supplied with feedstock,

generation of biogas remains a very suitable option for the generation of additional power to

alleviate peak power energy demand (Griffiths, 2013).

The biogas produced can be applied as electricity through the use of gas turbines or used as

gas. The electricity generated could potentially be fed into the national electricity grid if

sufficient and effective policies and legislations are in place to do so. Available incentives

and rebates make farm-scale biogas plants a very attractive option for farms looking to reduce

their carbon footprint and save on electricity bills (Griffiths 2013, Scharfy et al. 2017).

Government-subsidised rural biogas generation as is taking place in China and India is

however not implemented on a wide scale in South Africa as yet (SAGEN and SABIA 2016).

In addition, GreenCape states that as a liquefied petroleum gas (LPG) replacement, biogas

provides sufficient heating and electricity generation with a current market value of more

than R450 million, and a potential market of R18 billion (GreenCape 2017b).


23

2.4.2 Waste management in South Africa

In many Asian countries, waste is regarded a valued resource of renewable energy (Greben

and Oelofse 2009). The DEA have stated in their Environmental Outlook Report 2013 that

South Africa’s economic development, rate of urbanisation and population growth, have led

to the increased generation of waste requiring the implementation of effective programmes

and policies for waste management (DEA 2013, DEA 2016).

This makes the uninhibited generation of waste an unfortunate reality in South Africa, and

presents waste management as another significant human-derived obstacle to overcome in

terms of sustainability, potentially addressing goal 11 and 12 of the SDGs: sustainable cities

and communities (goal 11), and responsible consumption and production (goal 12) (UNDP

2017, SAGEN and SABIA 2016). The management of waste in a developing country such as

South Africa plays a key role in its sustainability status and the progress of a country (Msibi

2015), therefore the use of biogas digesters supports the development of South Africa’s

sustainability movement as it contributes to efficient waste management (Biogas 2013). With

the increasing costs of fossil fuel and electricity, there is a growing interest for biogas as a

source of affordable and renewable energy, as well as an effective waste management method

(Biogas 2013, GreenCape 2017c). In 2009, it was estimated that in South Africa, some 40 per

cent of waste generated consists of organic material that supplies biogas when digested

(Greben and Oelofse 2009).

Biogas can be used to supply energy in the form of heat, combined heat and power (CHP) or

fuel for vehicles or machinery. One of the significant benefits of using a biogas plant as a

renewable energy solution is its capacity to be situated at any location where waste feedstock

is available (SAGEN and SABIA, 2016). This makes it particularly suitable for rural areas

and agricultural areas.

The success of biogas digesters rely largely on the sufficient use of waste as feedstocks for

specific digesters (Biogas 2013). The WWF FEW report (Carter and Gulati 2014) states that

nine million tonnes of food is wasted every year (34 % of all food) and that energy lost

through this wastage has the potential to power Johannesburg for 20 years. It also stated that

agriculture production is the major sector where mostly organic waste is generated in South

Africa which, and if managed correctly, could be highly potential feedstocks for biogas

digester systems (GreenCape 2017b). Industry and mining can also supply feedstock (DEA

2009b) through wastewater or discharge, the biological treatment and discarding of solid


24

waste, and the burning of waste (NT 2013). Households, institutions and commercial

businesses could also contribute to waste streams.

A study done by Potgieter (2011) maintains that the potential of biomass as renewable energy

resource is the total energy value of all the different available types of biomass that can

realistically be transformed into bioenergy. The study found that the potential of biomass as

renewable energy resource is more than the annual consumption of primary energy in the

world.

A DEA report on national waste quantification and waste information systems, also lists

issues which show a continuation of challenges for effective waste management. These

challenges highlighted several shortcomings such as flawed data collection; a lack of

compliance and enforcement capacity; a lack of incentives to reduce, recycle or reuse waste;

a lack of stakeholder education and awareness; a lack of local government support for waste

reduction; high waste management costs, and a shortage of suitable land available for waste

disposal (DEA 2009a).

Waste management in South Africa still largely relies on landfills which are the cheapest

waste disposal option due to low costs and availability of land. Methane emissions from

landfill sites in urban areas contribute about two per cent to the total GHG (greenhouse gas)

emissions in South Africa. However, these estimates for landfill methane emissions remain

uncertain as data on landfill depths, actual levels of waste disposed of, and the composition of

waste, remains lacking (NT 2013).

While municipal waste is not the largest waste volume in South Africa, it is the most

significant in terms of funding and the impact that it has on the day-to-day lives of ordinary

people (DEA 2009b). Municipal waste consists mostly of mainline recyclables, organics

(greens and garden waste), building rubble and non-recyclables (DEA 2013).

The National Environmental Management: Waste Act (No. 59 of 2008) (NEM:WA) and the

National Waste Management Strategy (NWMS) (2011) obliges municipalities to apply

alternative waste management actions in order to redirect waste from landfills (GreenCape

2017b). It is likely that 65 per cent of waste (totalling about 38 million tonnes) can be

recycled and put to alternative uses rather than being sent to landfills (DEA 2013). If based

on global trends, sending waste away from landfills could increase revenue from this sector:

in 2014, the Department of Science and Technology (DST) projected that an extra R17


25

billion/year worth of resources could be made accessible if 100 % of the identified waste

streams could be recycled (GreenCape 2017b).

It is predicted that by 2019, South Africa is aiming to reach the target of 20 % waste division

(DEA&DP 2015). For the Western Cape this means diverting 1.5 million tonnes per annum,

of which 800 000 tonnes are municipal solid waste (DEDAT 2016). This will not be easily

done, as the implementation of alternative waste management is relatively expensive due to

the initial capital costs that usually stem from the need for new infrastructure, and will be a

financial constraint based on current budget and location (GreenCape 2017b).

National legislation changes and the potential provincial goal to ban the landfill of organics

by 2026 are supporting the growth of organic waste beneficiation (GreenCape 2017b,

GreenCape 2017c). This will result in the remaining waste largely being dry recyclable waste

with less risk of contamination and also making more organic waste available for possible

anaerobic digestion process (GreenCape 2017b). Inhibiting factors of this process currently

are policies and legislations prohibiting the reuse of food waste in South Africa (Von

Bormann and Gulati 2014).

3.0 Anaerobic digestion as a sustainable strategy to meet energy demands and waste

management challenges

Anaerobic digestion (AD) is simple biological process which produces biogas via the natural

anaerobic bacterial decomposition of organic material including plant material, animals and

their wastes and waste water (Dennis and Burke 2001, Arbon 2005, Shah et al. 2014, Biogas

2013, GreenCape 2014, GreenCape 2017c). AD uses the same biological processes, but under

the controlled conditions of a digester system, that happen at landfill sites (Arbon 2005).

The four-stage process (Figure 2) of hydrolysis, acidogenesis, acetogenesis and

methanogenesis, occurs in a warmed and sealed biogas digester tank where bacteria ferment

organic matter in oxygen-free conditions to produce biogas and digestate. The organic

material used is often referred to as feedstock. Biogas digesters can operate on small, medium

or large scale (APPENDIX B). Figure 2 illustrates biogas digesters system used for raw

fertiliser production, electrical energy generation and heat energy generation. (Source:

Dussadee et al. 2016).

AD has been used for more than a century to stabilise municipal sewage and many other

types of industrial waste (Dennis and Burke 2001). Mostly wastewater treatment at


26

municipality plants uses AD to transform solid waste to gas. The anaerobic process

significantly reduces the pathogens present in the slurry and removes many of the odorous

compounds (Dennis and Burke 2001).

Figure 2: Illustration of the four stages of the anaerobic digestion process

(Source: Dussadee et al. 2016).

Biogas produced is a naturally occurring blend of methane CH4

(50–75 %), carbon dioxide CO2 (25–45 %), hydrogen sulphide H2S (0-3 %), hydrogen H2 (0-

1 %), carbon monoxide CO (0–2 %), nitrogen N2 (0–2 %), ammonia NH3 (0-1%), oxygen

O2 (0–2 %), and water H2O (2–7 %) (Shah et al. 2014). Biogas is a colourless and odourless

gas that burns with a clear blue flame and is in that sense similar to LPG gas (Ghimire 2013,

Nyns et al. 2014). However, these values may vary as the percentage amount per compound

varies for different feedstocks used.

Once generated and stored, biogas presents a flexible alternative for non-renewable energy

sources and has mainly been used around the world for household cooking and heating, as

well as for gas lamps and absorption refrigeration systems. Biogas also has many other

significant domestic and industrial uses. This is particularly true for rural areas, where the use

of biogas can replace the burning of wood for fuel for cooking and heating leading to


27

increased health and environmental benefits (Biogas 2013, Msibi 2015). Its use to power

electric generators is also well established especially in some European countries and in

North America (Dennis and Burke 2001).

It is estimated that one cubic metre (1 m3) of pure bio-methane contains approximately

10 kWh of chemical energy (Dillon 2011). Biogas contains approximately 60 % bio-methane

and therefore 1 m3 of biogas comprises about 6 kWh of chemical energy (Biogas 2013). A

co-generation engine is used to convert this to electrical energy, to produce both heat and

electricity. Other studies have also found that by analysing the production of thermal energy

in gas boilers and the production of both thermal and electrical energy in related units,

1 m3 of biogas in associated production of energy, 2.1 kWh of electrical energy and 2.9 kWh

of heat are obtained (Arbon 2005).

The average efficacy of methanogenesis alone produces approximately 0.24 m3 of methane

from 1 kg of dry organic matter. One cubic metre of biogas with the calorific value (relating

to the amount of energy contained) of 26 MJ /m3 may replace 0.77 m3 of natural gas with

33.5 MJ calorific value, 1.1 kg of hard coal with 23.4 MJ calorific value, or 2 kg of firewood

of 13.3 MJ calorific value (Arbon 2005). These values may only give a broad idea as the

biogas-to-energy technology has improved since 2005, when the data above was determined.

These energy values are based on averages and ultimately prove the potential of biogas.

However, these energy values may differ as they are dependent on feedstock quality and type,

as well as type of digester mechanisms used.

Additionally, its production creates digestate (high-quality nutrient-rich soil conditioner) and

enables the production of petrochemical substitutes. This makes biogas a suitable

replacement of fossil resources on many levels (Dennis and Burke 2001, Culhane 2017).

Digestate has physical and chemical characteristics that are comparable to manure compost

and is the by-product of heat and methane production in a biogas plant (Torquati et al. 2014).

Digestate, whether in a liquid or solid form, has a high mineral nitrogen (N2) content and

other macro- and microelements that are needed for plant growth and has potential to be

converted to a fertiliser in South Africa (Dillon 2011). See Figure 3 (Source: Dillon 2011).

The most important environmental benefit of agricultural biogas however probably lies in the

contribution it can make to reduce (CH4) emissions arising from the natural decay of organic

matter, and in the overall decrease in carbon dioxide (CO2) emissions that can be brought


28

about by the use of alternative energy sources instead of conventional fossil fuels (Torquati et

al. 2014).

However, according to Torquati et al. (2014) these benefits are not easily measured.

Obtaining renewable energy is a particularly complex process, as it involves different types

of biomass as well as a variety of chemical, physical and thermal processes used by different

digestion technologies. Biomass feedstock can vary from municipal wet (organic) waste and

food waste to agricultural crops and harvesting residues including manure. Similarly complex

are the decisions that have to be made about the best ways to use the digestate and biogas

produced. This complexity thus presents many challenges to analysing the energy and

environmental benefits of biogas production (Torquati et al. 2014).

Figure 3: Illustration of anaerobic digester and biogas generating system used for raw

fertiliser production, electrical energy generation and heat energy generation. (Source: Dillon

2011)

3.1 Feedstock importance and availability

When compared to wind and solar as renewable energy technologies, biogas digesters do not

require a primary resource such as wind or sun, but requires a secondary resource referred to

as feedstock (SAGEN and SABIA 2016). Feedstocks are essential to ensure successful

anaerobic digestion in biogas digesters (GreenCape 2017c). For a particular biogas digester to

run productively, it is vital that feedstocks are correctly used and managed. Depending on


29

their organic content different feedstocks generate different amounts of methane. The

methane content of the biogas reveals its energy value. If the feedstock quality is low, the

biogas produced will have lower methane content, resulting in lower energy value (NNFCC

2016). Maize and grass fodder, for example, produce more methane per m3 of biogas than

livestock manure, while livestock manure has greater potential than human sewage waste

(Dussadee et al. 2016).

It was stated by The National Non-Food Crops Centre (NNFCC) that in order for biogas

plants to be viable over its 10 to 20-year lifespan, consistent quality of feedstock is needed

(NNFCC 2016). What is more, as a digester needs to be fed constantly and consistently to run

productively for 24 hours per day, requiring that feedstocks must be accessible at all times.

The removal of digested sludge also involves regular management as digestate accounts for

up to 95 % of the feedstock, and could lead to a digester malfunctioning if it is not removed

on a regular basis (NNFCC 2016).

If organic feedstock is allowed to naturally decompose it will lead to a decrease in the

methane production (NNFCC 2016). The feedstock should thus be fresh, but also of certain

water content. Feedstocks left outside for long periods of time could be rendered less

effective because of moisture loss. It is vital for the success of any biogas digester plant that

these plants are fitted out with adequate feedstock storage facilities to ensure consistency and

quality of stocks (NNFCC 2016).

While all organic material could potentially be used to produce biogas, not all possibilities of

organic matter production are relevant to the South African industry. The few existing large-

scale biogas digester systems currently operational in South Africa are mostly used as a

problem-solving mechanism and mainly relay solid and hazardous waste from landfills. In

contrast, international government incentive programmes have enabled many more feedstock

avenues to be thoroughly utilised at larger scale biogas digester systems in other places in the

world (SAGEN and SABIA 2016).

This approach is not necessarily relevant to South Africa, as water scarcity and the reliance

of a significant number of people on subsistence farming impacts the availability of

feedstocks. For example, growing carbohydrate-rich maize as a feedstock for biogas digesters

is not necessarily viable in South Africa, and is more appropriate to developed countries such

as the United States of America or Germany (SAGEN and SABIA 2016). It is thus essential


30

when considering South Africa’s biogas digester industry, or when constructing an ideal

conceptual model, that realistic and available feedstock avenues should be explored.

3.2 Feedstock types in South Africa

The following feedstock types, agricultural crop waste, manure (poultry, cattle and dairy

farms/feedlots), abattoir waste, municipal solid waste and sewage are seen as the feedstocks

with the highest potential for a country such as South Africa (Smith 2011, Msibi 2015,

SAGEN and SABIA 2016).

3.2.1 Agricultural crop waste

In South Africa a number of agricultural outputs exist, and agricultural waste in this study

specifically refers to crop and plantation wastes such as vegetables, sugar cane and fruit, and

exclude manure and abattoir waste. These outputs are typically seen as waste streams that

could be redirected as resources for other farms and are thus not likely to be redirected

towards anaerobic digestion. Examples are fruit pulp used for livestock feed, and compost

used for fertiliser (SAGEN and SABIA 2016). The potential for the implementation of

anaerobic digestion in South Africa therefore only becomes a possibility when agricultural

waste becomes available for bio-digestion and is not redirected for alternative uses and/or

other purposes. It is against this background that SAGEN and SABIA (2016) believes that

anaerobic digestion has the highest potential to be implemented on farms that could benefit

from reduced electricity and/or heat costs, and costs incurred with waste treatment, storage

and transportation.

Van der Merwe (2014) maintained that crop remains are often classified as so-called

production residues, and are produced as an important part of the commercial production of

agricultural crops, but not as the end product. This can include bruised, undersized or

misshapen fruit and vegetables separated on the farm or in a pack-house that are regarded as

unsuitable for sale; or vegetable and fruit toppings, roots and leaves that are removed as

before sale (Van der Merwe 2014).

Van der Merwe (2014) further states that while there are some agricultural products that are

not necessarily effective for AD, it is often found that its by-products are suitable for AD. An

example is sugarcane, where the by-products from sugar-milling such as wastewater and


31

filter cake are rich in organics and may be regarded a valuable feedstock for biogas

generation (Magama et al. 2015). Sugarcane itself is not a viable feedstock as it consists

mostly of water with 15 % fibre and 15 % sugar; once the sugar water has been removed

from the cane, the remaining fibre is burnt to yield steam and electricity for on-site use (Van

der Merwe 2014) and therefore an AD technology is not required.

With South Africa having a large wine industry, some studies have considered grape pomace

as a potential feedstock for the production of biogas, especially in the Western Cape where

most of the wine industry is based. However, a study found that the viability of using a

biogas digester is determined by the finances of the facility and the availability of organic

feedstock throughout the year (Dillon 2011). The study established that as the wine and grape

industry is dependent on seasonal production, generation of electricity from grape pomace for

a single farm alone is not sustainable. One metric tonne of grape pomace will yield about 230

m3 of biogas; one tonne of grape pomace should produce approximately 828 kWh of

renewable electricity. The study concludes that joint ventures within the wine industry could

result in communal digesters servicing surrounding wineries, making it more viable as a

sustainable solution to winery waste (Dillon 2011).

3.2.2 Manure (poultry, cattle and dairy farms/feedlots)

Manure and abattoir wastes are both so relevant in the South African biogas industry that

they deserve separate explanations and are for this study not included under a combined

heading of agricultural wastes. DAFF (2015) estimated that in 2002 South Africa

approximately had 14 million cattle: 1.6 million commercial dairy farms, 6.6 million beef or

dual purpose cattle and 5.7 million communal cattle. As an agricultural by-product from dairy

farms, feedlots and other livestock farms (such as chicken farms), manure waste is often used

as an untreated fertiliser or stored in waste lagoons creating enormous potential for biogas

generation (Dennis and Burke 2001). The use of manure for on-site anaerobic digestion could

considerably improve the handling process and contribute to the elimination of potential

negative environmental impacts, such as the spread of unwanted pathogens and the

accumulation of harmful nitrates in the water table (SAGEN and SABIA 2016). In return, the

electricity and heat produced on site could help to bring down running costs and reduce the

farm’s dependence on the grid (Baltic Deal 2012). The digested sludge as by-product could


32

be used as a treated soil conditioner on the specific farm or supplied to commercial and

domestic agricultural fertiliser producers.

A study by Msibi (2015) stated that availability of feedstocks for domestic low-income

households in South Africa is one of the key factors when considering domestic scale biogas

digesters. When referring to low-income-domestic/rural/small scale application of manure,

Msibi (2015) established that where enough cattle and pig manure are available, a substantial

number of households could benefit from community digesters but that it will be more

feasible for community digesters to be fed a mixture of sewage and waste such as pig and

cattle dung. However, Msibi (2015) maintained that due to the small average number of

chickens kept by a low-income South African household, chicken manure alone is not enough

to operate a biogas digester on a small domestic scale.

On the other hand, the South African Poultry Association (SAPA) stated that the South

African poultry industry totalled at 142 million birds in 2014 (SAPA 2014). Chicken manure

has a high production potential of 80 L biogas/kg when compared to cow manures and faeces

producing 40 L of biogas/kg (Dillon 2011, Belostotskiy et al. 2013). With this said it is clear

that the poultry industry as a potential feedstock supplier for AD processes holds promise for

community-based and medium to larger scale biogas digester industries in South Africa, and

should not be overlooked.

3.2.3 Abattoir waste

The generation of power in South Africa is not cheap, and recent studies have shown that

electricity is one of the biggest expenses at an abattoir (Swanepoel 2014). The limits placed

in South Africa on the disposal of hazardous abattoir waste, together with the benefit of

generating heat and electricity that are tailored to the abattoir’s operational requirements,

creates an excellent opportunity for abattoirs to implement anaerobic digester implementation

(SAGEN and SABIA 2016). Due to the large amounts of organics that abattoir wastewater

contains NEM:WA (2008) restricts this wastewater from entering conventional wastewater

treatment plants. Similarly Neethling (2014) stated that burning and sterilising waste has been

limited because of threatening negative environmental impacts and the risks of pathogens

spreading. Treating, storing and transporting wastes to landfills that accept such hazardous

materials could potentially increase the costs of running an abattoir. Swanepoel (2014) found

that intestines (gut contents) and manure proved to be the abattoir waste with the highest


33

potential and efficiency for biogas generation. Swanepoel (2014) further maintains that South

African abattoirs slaughter at a rate of 150 units per day, generating about 12 T of by-

products. A biogas plant with that amount used as feedstock may generate about 115 kWh of

electricity/day (Van Rooyen 2013). A study by Uduak et al. (2012) further confirmed that

implementing a biogas plant using abattoir wastes as fuel could prove to be cost-efficient.

GreenCape (2017c) also stated that medium scale (>50kWe; <1MW) biogas facilities at

abattoirs showed to be financially viable at the middle to high end of the size range, when

there are high waste management costs and full utilisation of energy on-site.

3.2.4 Municipal solid waste

Organic food waste is divided at source to separate domestic, industrial and commercial

waste streams, and can be used for on-site composting or directed to landfills. Organic food

waste used as feedstock for an anaerobic digester has the potential to generate electricity

and/or heat, while the digested sludge could be applied as fertiliser.

Similar to abattoirs, commercial beverage and food production set-ups such as cheese

factories, breweries and fruit and vegetable processing facilities could use their organic

wastes to produce their own heat and electricity on site (Swanepoel 2014, SAGEN and

SABIA 2016). Recent studies have stated that less strict waste laws for these waste streams

(as opposed to abattoir waste), result in most of these waste streams being sent to landfills

(SAGEN and SABIA 2016). The study also found that the implementation of anaerobic

digestion at operations such as these could reduce transport costs to landfills and costs

incurred for heat and electricity generation. On a larger scale, it would significantly reduce

the amount of waste redirected to landfills (SAGEN and SABIA 2016).

3.2.5 Sewage

Biogas produced at waste water treatment works (WWTW) could be used to provide

electricity for the up- and downstream treatment processes. Waste water is a well-known

feedstock in the biogas industry around the world as sewage sludge has a high methane

volume in relation to biogas produced from other feedstocks (Bachman 2015). The main

feedstock for anaerobic digestion (AD) in WWTW is sewage sludge. Biogas production at a

WWTW starts with sewage sludge pre-treatment, followed by AD and biogas production, and

ends with post-treatment of the digested sludge and the gas produced (Bachman 2015). Like


34

all other biogas by-products, the sludge has no smell and is nitrate-rich making it suitable to

be used as agricultural fertiliser (SAGEN and SABIA 2016).

Conventional wastewater treatments use AD to reduce the pathogen load and water content of

the sludge and to remove odours (GIZ & SALGA 2015). WWTWs that do not have the

conventional digestion processes in place would need a greater capital input to establish a

biogas unit, and for this reason it will be necessary to evaluate the viability of such a WWTW

against its estimated economic benefits (GIZ & SALGA 2015a).

Rural housing developments, schools and clinics that are not connected to a wastewater

system could produce electricity or gas as fuel for cooking and heating purposes by using AD

to treat their sewage wastes. In addition, using AD could have the benefit of preventing

potentially dangerous pathogens from entering the groundwater (Msibi 2015, SAGEN and

SABIA 2016). One of the reasons why human excreta has not taken off as possible feedstock

is that the World Health Organisation has stated that pathogen reduction by mesophilic AD is

insufficient to allow subsequent use of human excreta as potential fertiliser derived from

biogas digesters (Bond and Templeton 2011).

3.3 Potential use of digestate as fertiliser

Digestate, also sometimes referred to as biogas slurry, is the by-product of methane and heat

production in a biogas plant using organic waste (Surendra et al. 2014). Depending on the

biogas technology used, digestate could be in either a solid or a liquid form. Digestate

comprises many macro- and microelements required for plant growth such as nitrates,

ammonia and phosphates. Mineral nitrogen (N2) is available in the form of ammonium. The

availability of nitrogen (N) for agricultural crops is the most common factor that limits

growth (Makádi et al. 2012). This makes digestate a beneficial source of nutrients and an

effective fertiliser for crops. In addition, the organic elements of digestate can influence the

biological, chemical and physical characteristics of soil (Makádi et al. 2012).

The solids and liquids of the digestate are mechanically separated, so that the solid part can

mix with the lignocellulosic substrate in the compost tank. The liquid part, when biologically

stabilised, can be used as fertiliser either with drip fertigation or by direct application into the

ground. In the composting system, the digestate is constantly stirred and aerated for three to

four months in an effort to lessen the moisture content and to form a stable ready-to-use


35

fertiliser mix (Torquati et al. 2014). Digestate can also infiltrate the soil faster than normal

fertiliser reducing the risk of nitrogen losses (Surendra et al. 2014).

The quality of digestate as a fertiliser is determined by the input materials and the retention

time (Makádi et al. 2012). A longer retention time results in a lower organic content, because

of more effective methanogenesis (Szűcs et al. 2006). According to Burton et al. (2009) the

typical composition of digestate is predominantly cellulose, lignin, biomass sludge and

inorganic components. In the absence of pathogens or potentially toxic elements, the

digestate makes an ideal bio fertiliser, often after a period of aerobic treatment to degrade

lignin and oxidise ammonia to nitrate (Burton et al. 2009).

The benefit of digestate use is its ability to make nutrients available within the crop rotation

from autumn to spring, when crop nutrient demand grows (Möller et al. 2008). The higher

nitrogen content of digestate in comparison to compost is the result of the nitrogen

concentration effect due to carbon degradation to CO2, CH4 and N2 preservation during AD

(Tambone et al. 2009). Digestate also contains more phosphorus (P) and potassium (K),

assumed to be more readily available than that of composts (Börjesson and Berglund 2007,

Tambone et al. 2009) making it more suited as a supplement in soils missing these

macronutrients. The typical ratio of phosphorus to potassium in digestate is about 1:3 which

is very good for rape and grain.

Table 4 illustrates a summary of the nutrient contents of the digestate compared to other

organic manure and vermicompost. Vermicomposting is another form of sustainable

composting making use of a natural ecological decomposition process. Vermicomposting

makes use of various worm species to create a varied mix of decaying vegetable or food

waste, bedding materials and vermicast (Surendra et al. 2014).

Table 4: Nutrient content of important organic manure (Source: Surendra et al. 2014)

Organic

manure

Organic

matter (%)

C:N N2(%) P2O5 (%) K2O(%)

Farm yard

manure

25-55 15-20 0.40-0.80 0.60-0.82 0.50-0.65

Biogas slurry 60-73 17-23 1.50-2.25 0.90-1.20 0.80-1.20

Vermicompost 9.80-13.40 - 0.51-1.61 0.19-1.02 0.15-0.73

3.3.1 Effects and application of digestate

Depending on soil types, digestate has a very complex effect on the chemical, physical and

biological properties of soils (Makádi et al. 2008). It can be applied as a fertiliser to enhance


36

soil quality (Schleiss and Barth 2008) as digestate is suitable to sustain nutrient levels in soils

and soil fertility (Tambone et al. 2007).

Odlare et al. (2008) and Fuchs and Schleiss (2008) report that they have not found

noteworthy changes in soil pH where digestate had been applied even though an increase of

the soil pH is assumed because of the alkaline nature of digestates. However, the pH of

digestate may fluctuate as digestate could comprise several acidic compounds (e.g. Gallic

acid), making the regular monitoring of soil pH necessary in cases of long-term use (Makádi

et al. 2012).

In comparison to the varied organic wastes that are available like sewage sludge, biogas

residue, compost and manures with and without mineral nitrogen, biogas digestate was found

to be more efficient for promoting microbiological activity in soils (Makádi et al. 2012).

Substrate induced respiration (SIR) increased with the high amount of easy-degradable

carbon that resulted from higher plant growth (Makádi et al. 2012).

The application rate of liquid or solid digestate depends on the nitrogen demands of the plant

and should be often used when plant nitrogen needs are high (Stinner et al. 2008). Because of

this high available nutrient content, the use of digestate brought about meaningfully higher

above-ground biomass yields in the case of winter and spring wheat compared to farmyard

manure and undigested slurry treatment (Stinner et al. 2008). Makádi et al. (2012) also found

liquid digestate treatment led to significantly higher yields of sweet corn and silage maize.

Digestate treatment also seems to effectively increase the protein content of plants (Makádi et

al. 2012).

The efficiency of a digestate is dependent on the composition of co-digested material, the

plant species treated and the methods of treatment; co-digestion of different organic materials

produces a more effective digestate (Möller et al. 2008). While crop yield is a very important

economical consideration in plant production, it is offset by the increasing demand for higher

quality foods. Digestate application in solid or liquid form could significantly improve the

quality of foods without negatively impacting on the environment, which is very significant

for promoting a sustainable environment and healthy life (Makádi et al. 2012).


37

3.3.2 Digestate regulation processes in other countries

Sustainable recycling of organic wastes requires clear regulations concerning wastes to be

recycled and the methods used, and these regulations differ from country to country (Makádi

et al. 2012).

In Hungary, the digestate is seen as non-hazardous if it does not comprise sewage or sewage

sludge, while if these materials are present the, digestate utilisation will depend on the quality

of the supplied material (Makádi et al. 2012). In Switzerland the digestate which fits the

limits is used as soil conditioner and fertiliser in so-called bio-agriculture (Makádi et al.

2012). The BSI PAS110:2010 (British Standards Institution Publically Available

Specification) digestate quality assurance scheme is applied in Scotland (SEPA 2017), and if

a digestate fulfils the quality requirements, usage criteria and certification system, the

Scottish Environment Protection Agency (SEPA) does not apply waste regulatory control. In

Germany the origin of the input materials controls the quality of the digestate, and digestates

have to satisfy the minimum quality requirements for liquid and solid types determining the

minimum nutrients and the maximum pollutants (such as physical contaminants, toxic

elements and pathogen organisms) that may be present in the digestate (Siebert et al. 2008).

3.3.3 Potential in South African fertiliser industry

South Africa is a net importer of fertilisers, importing all our potassium, as well as 60 % to 70

% of our nitrogen (N) requirements. The South African fertiliser industry is thus fully

exposed to world market forces while it functions in a deregulated business environment with

no import tariffs or government support. In this deregulated market, fertiliser prices are

affected by global prices, currency exchange rates (ZAR/USD) and transport costs (DAFF

2015). This subjects local prices to the same supply and demand drivers as in the

international industry. Most of the international fertiliser prices (USD/ton) increase annually

and due to the significant depreciation of the local currency, international fertiliser prices

increased even more (DAFF 2015).

While the properties of digestate makes it possible to use as fertiliser and renders it suitable

for soil improving (Makádi et al. 2012), the use of digestate as potential fertiliser has

economic and environmental benefits because it could lead to a situation where much less

artificial fertilisers could be required for plant production. A study by Gautam et al. (2009)

found an annual savings of 4 329 T N, 2 109 T of phosphorus and 4 329 kg potassium due to


38

the implementation of biogas digesters in Nepal to replace previously imported chemical

fertilisers with the organic form of digestate fertilisers translating into an annual saving of

approximately USD 300 000.

South Africa’s consumption of fertiliser experienced an increase from 2004 and a decline in

2005 and 2010 to approximately 350000 and 400 000 T respectively (DAFF 2016). The

Makádi et al. (2012) study found that digestate has a high amount of N2 particularly in the

form of ammonium which is available for plants, making it a suitable substitute for other N

fertilisers used in South African applications.

The alkaline pH of digestate could also make soils less acidic, which is seen as serious

problem around the world but especially in South Africa. Using digestate instead of artificial

fertilisers could further increase the productiveness of over-used and previously poorly

managed soil, ultimately contributing towards more sustainable agricultural practices in

South Africa (Makádi et al. 2012). The study by Makádi et al. (2012) concluded that the use

of liquid or solid digestate could significantly improve the quantity and quality of foods

through even nutrient supply, contribution to healthier lifestyles and well-being.

Figure 4 below illustrates the fertiliser composition in South Africa, showing that nitrogen

fertilisers seem to be the most-used fertilisers, followed by potassium and phosphorus.


39

Figure 4: Illustration of the fertiliser consumption in South Africa between 2005 and 2015 of

the three major fertiliser components: Nitrogen (N), Phosphorus (P) Potassium (K). (Source:

FERTASA cited in DAFF 2016)

However, caution must be taken as numerous studies have found that even if AD can reduce

microbial pathogens, the digestate may still not be completely safe to use as fertiliser

(Parawira 2009, Bond and Templeton 2011, Surendra et al. 2014). It is essential that proper

post-treatment of digestate is required prior to application as a soil conditioner/amendment to

ultimately prevent public health risks (Surendra et al. 2014). Examples of digestate post-

treatment methods are drying, composting, acticated sludge treatment, membrane filtration,

ammonia stripping, and vacuum thermal stripping on manure (Trémier et al. 2013, Törnwall

et al. 2017).

It is evident that there is a looming potential for biogas digester fertiliser production and use

in South Africa and that it is clearly something that the government and farmers should look

into as it contributes to a more sustainable farming approach for the country, not only in the

ecological sense, but also on economical and sociological levels.


40

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51

PAPER 1: INVESTIGATING THE POTENTIAL OF

BIOGAS GENERATION IN SOUTH AFRICA AS A

SUSTAINABLE PRACTICE, BY TAKING INTO

ACCOUNT THE STATUS, CHALLENGES AND

OPPORTUNITIES OF THE LOCAL INDUSTRY

Abstract

Biogas generation and utilisation has the potential to impact all three pillars of sustainability

namely environmental, social and economic, and could achieve what few other renewable

energy technologies do, which is to integrate waste management and energy technologies

(Biogas 2013, Bachmann 2015, SAGEN and SABIA 2016). For the purpose of investigating

the potential of biogas generation in South Africa as a sustainable practice, a literature review

was conducted, supported by face-to-face semi-structured interviews (Babbie and Mouton

2001), with among others representatives of the South African Biogas Industry Association

(SABIA) and GreenCape. This investigation indicated that the interest in the development of

medium and commercial-scale biogas digesters can be attributed to opportunities that the

biogas industry offer in terms of job creation, energy provision, carbon mitigation, organic

fertiliser production and waste management. The study found that the South African industry

is currently faced with challenges in terms of renewable energy generation and supply, lack

of government support, financial commitments involved in its development, skills shortages,

ethical challenges, limited water resources and sustainable access to waste as a biomass

source. The study also identified that innovative enablers exist that can promote the growth of

the industry. In further support of its potential, biogas generation can be a means to overcome

energy poverty and could contribute significantly to sustainable development in South Africa.

By applying enabling factors such as streamlining EIA processes and licencing requirements

and creating a market for surplus energy generated, biogas generation can provide tax relief

through the anticipated implementation of carbon tax; creating innovative solutions for waste

management and the organic fertiliser industry, while delivering ecosystem services such as

carbon sequestration in soils and improved water and soil quality and, ultimately, an increase

in food production.


52

Introduction

With a global drive towards a more sustainable future, two of the most significant man-

induced hindrances to overcome are unsustainable management of waste and access to a

secure supply of clean energy (SAGEN and SABIA 2016).

Biogas utilisation could potentially impact all three pillars of sustainability, namely

environmental, social and economic, and for this reason sustainability is defined in this paper

as: “The process of utilising and living within the limits of available physical, natural and

social resources in ways that promote social, ecological and economic sustainability all at

the same time, while allowing the living systems in which humans are rooted to flourish in

perpetuity” (UN 1987, DEA 2008, Nahman 2009, Kuhlman and Farrington 2010, Morelli

2011, Uwosh.edu 2017, Greencape 2017).

Biogas production via anaerobic digestion could achieve what few other renewable energy

technologies do as it integrates waste management and energy technologies (Biogas 2013,

GreenCape 2017b), and in so doing creates a promising pathway towards achieving

sustainable development. Biogas generation could ultimately reduce methane and carbon

dioxide, while addressing the social dynamics and requirements of a developing country;

promoting ways to reduce energy costs, provide waste management solutions and produce

organic fertiliser for own use or as an additional source of income (Biogas 2013).

In this paper, the potential of biogas utilisation in South Africa is evaluated against the

principles of sustainability, taking into account the status, challenges and opportunities that

the industry presents.

Materials and methods

For the purpose of investigating the potential of biogas generation in South Africa as a

sustainable practice, face-to-face semi-constructed interviews (Babbie and Mouton 2001),

were conducted with among others representatives of the South African Biogas Industry

Association and GreenCape, a non-profit organisation that drives the widespread adoption of

economically viable green economy solutions from the Western Cape. This information is

supported by the findings of a literature review.


53


In 2008, South Africa adopted the National Framework for Sustainable Development (NFSD)

that expresses the country’s vision for sustainable development and identifies strategic

interventions to re-direct South Africa’s development path (DEA 2008). In response to

growing pressures on the environment and its natural resources, the NFSD commits South

Africa to a long-term programme of resource and impact decoupling and identifies principles

and trends regarding sustainability, as well as actions to be taken (DEA 2013). Decoupling

refers to the ability of an economy to grow without the parallel increases in environmental

pressure. Key to NFSD is how this can be done through joint ventures and cooperative

governance practices (DEA 2013).

South Africa has a systems approach to sustainability, which is one where “…the economic

system, the socio-political system and the ecosystem are embedded within each other, and

then integrated through the governance system that holds all the other systems together in a

legitimate regulatory framework. Sustainability implies the continuous and mutually

compatible integration of these systems over time. Sustainable development means making

sure that these systems remain mutually compatible as the key development challenges are

met through specific actions and interventions to eradicate poverty and severe inequalities”

(DEA 2008, DEA 2013, DEA 2016). With the acknowledgement of the critical importance of

moving towards more sustainable development in South Africa, the use of anaerobic

digestion (AD) to generate electricity and to manage waste production could play a defining

role in sustainable development (Biogas 2013, DEA 2013, GreenCape 2017a, Tiepelt 2017).

GreenCape (2017a) regards the development of biogas industry as based on the triple bottom

line context of an African economy; measuring the impact of an investment in technology on

its social, environmental, and economic relevance and its relation to the concept of

sustainable development (Hammer and Pivo 2016).

2.0 Development of the biogas digester industry in South Africa

For a long time the South African biogas industry existed in a low-intensity state, a fact that

could be seen as evidence of its potential (SAGEN and SABIA 2016). The first example of a

biogas digester in South Africa was on a pig farm south of Johannesburg in the early 1957.

This was done by John Fry, who started producing biogas through using pig manure in very


54

simple 170 litre drums as digesters to run his six horsepower Lister engine (GIZ and SALGA

2015a).

While the Department of Energy (DoE) admits to the limited existence of both domestic and

commercial applications in South Africa (DoE 2015), South Africa was again one of the first

countries in the world to develop digesters as part of sludge management at waste water

treatment works (WWTW), with the first municipal digesters built as far back as in the 1940s

(GIZ and SALGA 2015a).

However, these were isolated incidences. Compared to other developed and developing

countries, South Africa has had a slow uptake of anaerobic digestion, both commercially and

rurally. Government-funded rural biogas implementation such as is seen in China and India

(also BRICS countries), has not been applied in South Africa, mainly due to intensive capital

investment requirements, slow and hindering legal processes and a lack of government

support (SAGEN and SABIA 2016).

In the late 1970s and early 1980s digesters were put to more active use at WWTWs. In 1998,

the Ceres Fruit farm digester was built followed by the Cape Flats biogas digester for

dewatering sludge in 2003 and the completion of a 1.5 MW digester at Marianhill in Durban

in 2010 (Mutungwazi et al. 2017). But, the focus was on sewage/sludge management and not

on the production of biogas, as the primary aim of the water works was to treat water, while

the digestion process provided an easy way to reduce the quantity and improve the quality of

the sludge. Here biogas was vented or burned as a by-product. While some plants used it to

incinerate all large particles removed from the waste water and others used the gas to heat up

the digesters, it was never really used to generate electricity (Tiepelt 2017). GreenCape

(2017a) maintains that while the majority of South African WWTW have anaerobic facilities,

the methane gas is mostly vented.

Tiepelt (2015) stated that a total of 700 digesters existed at the time; 40 % at wastewater

treatment works, 50 % small-scale domestic/rural digesters and that only 10 % were

commercial installations (SAIREC 2015). ESI-Africa (2016) contradicted this by reporting a

total of 300 registered biogas plants in 2016, of which only 50 were registered commercial

biogas plants larger than 100 kW. This indicated that the country’s biogas industry comprises

a growing number of privately funded projects on agricultural land with livestock, at

abattoirs, municipal wastewater treatment plants and in rural/domestic households (See Table

1). GreenCape (2016, 2017a) support this by stating that the main waste-to-energy projects


55

embarked on by the private sector are on a small to medium-scale, where the energy

(electricity, heat and/or gas) is generated for own use, or wheeled through the grid to a nearby

private buyer.

Table 1 shows the list of biogas digesters installed in different parts of South Africa by

different developers. These power output values give a close estimation of the biogas yield

achieved by a given digester since 1 m3 of biogas generally produces 6 kWh of chemical

energy (Arbon 2005, Biogas 2013, Mutungwazi et al. 2017).

Taking into account the slow but progressive movement towards renewable resource

incentives in South Africa, biogas power generation is now presenting a strong business

incentive (GIZ and SALGA 2015). The South African Local Government Association

(SALGA) and the South African-German Energy Programme (SAGEN), implemented by

Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ), entered into an agreement to

promote renewable energy at the local level of government. The collaboration aims to

strengthen the capability of local government to implement renewable energy projects and to

promote the facilitation of these projects within their areas of jurisdiction (GIZ-SAGEN

2015).

The Northern Waste Water Treatment Works (WWTW) of Johannesburg Water is an

example of this collaboration. Facing a steep increase in energy costs, Johannesburg Water

commissioned the upgrading of its sludge handling and digestion facilities at its five waste

water treatment plants to provide for the cleaning of biogas to use in electricity generation by

means of cogeneration methane gas engines. The initial installation at the Northern WWTW

was completed in 2012 and is capable of producing 1.1 MW of power for the treatment plant,

representing 18 % of the plant’s power requirements at the time (GIZ and SALGA 2015a).


56

Table 1: Illustrates location, developer name, substrate input and power output of biogas digesters installed in South Africa

(Source: GreenCape 2017c, Mutungwazi et al. 2017)

Area Developer Substrate input Power output

Alice in the Eastern Cape CAE/University of Fort Hare 4 000 m3 of dairy and piggery manure 2 × 132 kVa electricity

generators

Athlone Industria Alrode Brewery, Farm Secure Energy,

Wastemart, CEA/New Horizons waste to

energy

400 t of organic waste/day -

Bela-Bela Limpopo CAE Humphries Boerdery piggery Manure and waste water -

Belville EnviroServ Waste water treatment plant -

Bonnievale FarmSecure Carbon > 5 t bovine manure -

Bredasdorp iBert 4 t abattoir waste/day 100 kW

Cavalter iBert, EnviroServ/ Chloorkop LFG, 20 t abattoir waste/day 500 kW

Cullinan - 190 kW

Darling Uilenkraal CAE/Uilenkraal dairy farm Bovine manure 600 kW

Darling GrootPost FarmSecure manure Bovine manure -

Durban

Bisasar road LFG 3 500–5 000 refuse/day 6 MW

Marrianhill LFG, Ekhurleni LFG 550–850 t/day 1,5 MW



57


Grabouw Elgin Fruit and Juices, Ibhayi Brewery > 5 t of fruit waste/day 500 kW

Jan Kempdorp

iBert 5.5 t abattoir waste/day 135 kW

Jacobsdale - 150 kW

Johannesburg WEC/Northern Waste Water Treatment

Works

Sewage sludge 1,2 MW

Johannesburg Robinson Deep - 19 MW

Klipheuwel Reliance Composting 700 t organic waste/day -

Klipheuwel (Zandam) Farmsecure > 5 t of manure/day 600 to 700 kW

Mossel Bay Biotherm SA, Mossel Bay PetroSA Refinery waste water 4,2 MW

Newlands SAB Miller 4 500 m3 of wastewater/day 10 % of the plant's energy

demand

Paarl Drakenstein Municipality - 14 MW

Pretoria Bio2watt / Bronkhorstspruit Biogas plant,

Prospection Brewery

Manure 4,6 MW

Queenstown iBert 42 t mixed waste from a piggery/day -

Riversdale iBert 4 t abattoir waste/day 100 kW

Robertson Rosslyn Brewery - 150 kW

Springs BiogasSA / Morgan Springs Abattoir slaughter waste; organic waste 0,4 MW



58


Stellenbosch Veolia Water Technologies / Distell 1 000 m3 wastewater/day -

Stellenbosch Franschhoek Rhodes Food Group 35 kg per day (testing feedstock) -

Selectra Sewage, manure, fodder 0,5 MW

Selectra Sewage, manure, fodder 1 MW

Selectra Sewage, fodder, agricultural waste 1 MW

Table View Jeffares and Green / Bayside Mall 0,6–1 t of food waste/ day -

KZN

Khanyisa projects Manure from more than 2 cows, school,

organic and sewage waste

Rural cooking fuel

SANEDI Manure from more than 2 cows, school,


Rural cooking fuel

Eastern Cape (Alice, Fort

Corx and Melani villages),

Western Cape (Phillipi),

KwaZulu-Natal

AGAMA

Manure from more than 2 cows, school,


Rural cooking fuel

Gauteng Zorg Vegetable pulp and fodder 7 200 m3 methane



59

Tiepelt (2017) regards the Bronkhorstspruit Biogas Plant erected by Bio2Watt as the biggest

biogas project in Africa at a feedlot. Established in 2007, and awarded the South African

National Energy Association award for an energy project in 2015, Bio2Watt aims to produce

in excess of 50 MW of green energy in the country over the next ten years (Bio2Watt.com

2017). This company owns and operates the Bronkhorstspruit Biogas Plant (Pty) Ltd that first

contributed power to the national power grid in October 2015. It is regarded as an

independent commercial enterprise with an initial life cycle of 20 years, contributing to South

Africa’s energy mix. Its installed capacity is 4 MW (Bio2Watt.com 2017).

Biogas production in South Africa received a lot of attention up until 2013, followed by a

slight loss of momentum possibly due to both the policy and legislation hindrances and a shift

of interest towards solar and wind power. However, interest increased again during 2016 with

the new National Biogas Strategy 2015/2016 that had been drafted by the Department of

Energy (DoE 2016).

In January 2017, the Industrial Development Corporation (IDC), Clean Energy Africa,

WasteMart and Afrox, launched the multi-million rand New Horizons waste-to-energy plant

in Athlone, Cape Town (GreenCape 2017c). The plant will process over 500-600 tonnes per

day of municipal solid waste, amounting to about 10 % of the waste generated in Cape Town

(GreenCape 2017c, SAOGA 2017). This will be recycled and converted into various

products, including organic fertiliser, liquid carbon dioxide (CO2) and compressed bio-

methane (SAOGA 2017). According to Tiepelt (2017), these developments are indicative of

the growing interest in the commercial and large-scale use and implementation of biogas seen

in South Africa in the last five to six years. He ascribes this not to available incentives or

government rebates/subsidies, but to the tenacity of some project developers, combined with

the fact that many abattoirs and waste producers in South Africa face problems getting rid of

their waste.

Tiepelt (2017) believes that biogas generation at abattoirs, piggeries and feedlots in the

country can be seen as a waste management solution rather than a financial viable

replacement for Eskom bought electricity. This is supported by the GreenCape Market

Intelligence Waste Economy Report (2014) that states that the growth of small-scale biogas

projects in South Africa can be attributed to stricter environmental legislation regarding

waste disposal, and higher landfill fees coupled with the premium tariffs offered by Eskom

(AltGen, GIZ, SAGEN and GreenCape 2014).


60

SAGEN and SABIA (2016) reported that the rural sector has significant biogas potential due

to the fact that many communities are still without access to electricity, and even those with

electricity would prefer to use more cost-effective alternative fuel sources. The total potential

of electricity generated from biogas in South Africa from agricultural waste is estimated at

2 300 MW (GreenCape 2016), and it is predicted by Abbasi (2012) that by 2020, the largest

volume of biogas will come from farms and large co-digestion plants that are incorporated

into farming and food-processing structures. Households with enough waste or livestock are

also able to implement biogas digesters to generate an alternative energy source for heating

(Amigun et al. 2012).

There are several developers and governmental programmes implementing biogas projects

within the rural sector (see Table 1). The South African National Energy Development

Institute (SANEDI) is currently implementing the Working for Energy Programme, an

initiative focused on providing thermal energy and improving the quality of life in rural

communities. They are involved in three renewable energy initiatives, including the Melani

Village Biogas Expansion Project, the Illembe District and Mpufuneko Biogas Projects

(SAGEN and SABIA 2016). The lllembe District Biogas Project in KwaZulu-Natal has 26

operational digesters, and the Mpfuneko Biogas Project in Limpopo will comprise the

installation of 55 digesters. The Melani Village Biogas Project in the Eastern Cape has been

jointly developed with the University of Fort Hare, aiming to install 110 animal manure-fed

biogas digesters in the rural areas of the Eastern Cape specifically in villages around the

University of Fort Hare’s Alice Campus (UFH 2017). The specific focus is on making

energy more accessible and affordable to disenfranchised communities, and would thus

enable the villagers of Melani Village to use cheap and convenient biofuels. The project is an

ongoing and funded by the Department of Energy (DoE) by some R3.7 million through

SANEDI, their subsidiary (UFH 2017).

A number of developers are also active in the rural/small-scale sector including BiogasPro,

Agama and BiogasSA (SAGEN and SABIA 2016). Other small-scale digesters that have

been in operation before 2013 include a CAE installation of 30 kW at Humphries Boerdery

(Bela-Bela), and iBERT installing four small-scale biogas digester; Abattoir-Jan Kempdorp

(100 kW), Cullinan (190 kW), Robertson (150 kW) and Jacobsdal (150 kW). BiogsaPro

Agama has installed 320 small-scale units to date. Their projects are mostly located in the

Western Cape with some in the provinces of the Eastern Cape and KwaZulu-Natal (SAGEN

and SABIA 2016).


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3.0 Biogas potential in terms of energy demands and waste management in South Africa

3.1 Biogas generation as a strategy to address energy demands in South Africa

The Department of Energy (DoE) is assigned to ensure the sustainable and secure delivery of

energy for South Africa’s socio-economic development. Its National Development Plan

(NDP) foresees that South Africa will, by 2030, have an energy sector that promotes

economic growth and development through sufficient investment in energy infrastructure. It

anticipates that at least 95 % of the populace will have access to grid or off-grid electricity.

The intention is that gas and other renewable resources like solar, wind, and hydro-electricity

will be present as feasible substitutes to coal, and will supply at least 20 000 MW of the

additional 29 000 MW of electricity that will be required by 2030 (DoE 2015). This is

imperative as the energy mix should take into account its potential environmental impact and

should address sustainability by amongst others mitigating the effects of climate change

(DEA 2017). The South African government has also committed to a 34 % reduction in

greenhouse gas emissions by 2020 (Teljeur et al. 2016). GreenCape (2017a) believes that

biogas generation has the potential to save on carbon emissions especially when used as an

alternative fuel for operating machinery.

Since 2007 and until August 2015, South Africa had faced an unprecedented supply crunch in

the electricity sector that resulted in the country being unable to meet peak electricity

demands (Teljeur et al. 2016). The World Wide Fund for Nature’s (WWF) Food Energy

Water (FEW) report specifies that energy is a major element in the competitiveness and

sustainability of the farming sector (Carter and Gulati 2014) and unsustainable consumption

and production patterns due to the recurrent electricity crisis in South Africa have resulted in

huge economic and social costs for the country emphasising the need innovative use of

energy sources (Teljeur et al. 2016). South Africa also has a very specific electricity load

profile that does not necessarily match the period of highest solar energy generation, nor does

wind energy profiles fit in predictably with this demand profile (Griffiths 2013). This leaves a

gap for biogas electricity generation to alleviate peak hour demand. As long as the plant is

maintained and correctly supplied with feedstock, generation from biogas is not dependent on

any external conditions, making it a very suitable option (GreenCape 2017a, Griffiths 2013).

In addition, available incentives and rebates make farm-scale biogas plants a very attractive

option for farms looking to reduce their carbon footprint and save on electricity bills (Biogas

2013, Griffiths 2013, GreenCape 2017a, Scharfy et al 2017) while South African developers


62

are also looking at heat generation and the production of compressed natural gas to address

the needs of the growing duel fuel systems market (GreenCape 2017a).

3.2 Biogas generation as a strategy to address waste management in South Africa

The uninhibited generation of waste is an unfortunate reality in South Africa and across the

world. The DEA recognises in their Environmental Outlook Report 2013 (DEA 2013) that

economic development, a growing populace and increased urbanisation have resulted in the

generation of so much waste that biogas digesters will be needed for its management. Waste

management in South Africa still largely relies on landfills which are the cheapest waste

disposal option due to low costs and availability of land, with 90,1 % of waste generated

being disposed of to landfill in 2011 (DEA 2012, GreenCape 2017c). The National

Environmental Management: Waste Act (No. 59 of 2008) (NEM:WA 2008) and the National

Waste Management Strategy (NWMS) (2011) mandate municipalities to implement

alternative waste management to divert waste from landfill and minimise environmental

degradation (GreenCape 2017b).

One of the distinct advantages of a biogas plant is its ability to be located anywhere where

waste feedstock is available enabling it to play a significant part in the sustainability progress

of a country by contributing substantially to efficient waste management (Biogas 2013, Msibi

2015, SAGEN and SABIA 2016). This makes it particularly suitable for rural areas as the

agriculture sector generates mainly organic waste that could be used as feedstock (GreenCape

2016, GreenCape 2017b).

It is estimated that in 2009, 40 % of waste generated in South Africa comprised organic

matter which, when digested could supply biogas (Greben and Oelofse 2009), while the DEA

in 2012 estimated that 65 % of waste (approximately 38 million tonnes) is recyclable and

could be redirected from landfills to be repurposed (DEA 2012). The WWF FEW report

(Carter and Gulati 2014) states that nine million tonnes of food is wasted every year (34 % of

all food) and that energy lost this wastage could potentially power Johannesburg for 20 years.

Inhibiting factors of this process currently are policies and legislations prohibiting the reuse

of food waste in South Africa (Von Bormann and Gulati 2014).


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4.0 Opportunities and benefits of biogas generation in South Africa

The potential of small to medium-scale biogas digesters (APPENDIX B) to contribute to

sustainable development by providing a variety of socio-economic benefits, such as a

diversification of energy supply, enhanced regional and rural development, the creation of a

domestic industry and employment opportunities, and a wider variety of waste management

options is widely recognised (Rio and Burguillo 2008, Mshandete and Parawira 2009,

NERSA 2013, SAGEN and SABIA 2016, BiogasSA 2017, GreenCape 2017a). Small-scale

biogas digesters are also shown to especially beneficial in rural areas of southern Africa

where poverty levels are very high and where organic waste is generated that could be used

as a potential feedstock (Smith 2011, Amigun et al. 2012, GreenCape 2016, GreenCape

2017a). Ecosystem services that are potentially delivered in these rural communities are

increased carbon sequestration in soils altered with digested organic waste, improved water

quality, reduction of pollutants, and ultimately an increase food production (Ji-Quin and Nyns

1996, Mtambanengwe and Mapfumo 2005, Fonte et al. 2009, Onwosi and Okereke 2009,

NERSA 2013). Indirect carbon sequestration can also be attained through reduced carbon

losses due to reduced deforestation when household fuel is substituted by methane produced

AD (Lantz et al. 2007, Mwakaje 2008).

Many of these benefits are directly relevant to the Millennium Development Goals of

reducing poverty, promoting gender quality, promoting health and environmental

sustainability (UN 2015) and ties in with the Sustainable Development Goals (see

APPENDIX A) of the United Nations Development Programme (UNDP 2017).

4.1 Meeting rural energy needs and enhancing quality of life

Biogas has significant potential to meet South Africa’s energy needs through amongst others

simple installations in rural areas that could produce enough energy for cooking and heating,

and could be expanded to community-based or commercial biogas generation efforts (Biogas

2013, GreenCape 2017a). Installations such as these can lead to reduced levels of indoor

smoke, better lighting and creation of employment for local people (Amigun and Von

Blottnitz 2010). Msibi (2015) states that the complete substitution of fuel wood as a source of

energy with biogas could result in cost savings of R1 808 per household per year, which is

8,6 % of the household income and translates to a gross national annual cost saving of up to

R4-5 billion. The potential for the improvement of human well-being is thus significant.


64

4.2 Incentives and rebates in renewable energy generation

Policy and legislation has been a heated point of discussion in the field of biogas in South

Africa, especially with the implementation of tax rebates in the renewable electricity

generation with great disputes between the solar, wind and biogas electricity generation fields

(Camco Clean Energy 2012, NT 2013, NT 2014, NT 2015, SAGEN and SABIA 2016).

ESI-AFRICA (2016) states that the prevailing biogas feed-in tariff and a positive swing in

current environmental legislation which encourages the establishing of biogas plants, i.e. the

National Environmental Management Act (NEMA), the National Environmental

Management: Waste Act (NEM:WA), the National Environmental Management: Air Quality

Act, the National Waste Management Strategy (NWMS) and the Income Tax Act

Amendment 12L (Cleaner Development Mechanism) all serve to create conditions that

stimulate local biogas producers and may attract foreign biogas producers to the South

African market. The establishment of the Southern Africa Biogas Industry Association

(SABIA) further emphasises the expectation of the growth of the biogas industry in the

country (ESI-AFRICA 2016).

On a commercial and industrial scale, ESI-AFRICA (2016) projects that biogas generation in

South Africa has the potential to displace 2 500 MW of grid electricity, which is equal to the

size of Eskom’s Arnot coal-fired power station in Mpumalanga that was commissioned in

1975. According to The Market Intelligence Report (GreenCape 2016) biogas provides

heating and electricity generation potential with a current market value of more than R450

million, and a potential market of R18 billion; compared to solar-thermal which currently has

an industrial-scale installations value of about R100 million and a R3,7 billion potential

market for agri-processing in South Africa.

The joint rebate programme of Eskom and the Department of Trade and Industry (DTI)

together with the grants and better interest rates from the Industrial Development Corporation

(IDC) that provides for a low prime loan for green technology investments (Griffiths 2013,

Ruffini 2014, Tiepelt 2017), substantially enhanced the financial feasibility of biogas projects

in South Africa (GreenCape 2017c).

Furthermore, the Eskom Integrated Demand Management (IDM) offers an incentive for

reduced consumption under their Standard Offer Programme (SOP). In 2013, the IDM

proposed that for every kWh generated by a biogas plant in South Africa between 18h00 and

20h00 weekdays for the first three years of operation, Eskom will contribute R1.20 (Ruffini


65

2014). While this is not a big contribution to small-scale digester owners as their kWh

production is much lower than large-scale plants, it could play a role in the alleviation of

poverty by promoting domestic well-being through the growth of small-scale digesters as

seen in Asia (Zhu 2006, Bond and Templeton 2011, Smith 2011).

4.3 Carbon mitigation potential

Opportunities that are created for carbon mitigation are seen as one the key benefits and

motivations for the development of the biogas industry in South Africa (Tiepelt 2017). South

Africa is responsible for approximately 1.1 % of global greenhouse gas (GHG) emissions and

its emissions have increased by 24.9 % between 2000 and 2010 (Biogas 2013). Although the

waste sector adds only about 2 % to the total GHG emissions, it also presents a chance for

energy recovery and improved waste management practices (DEA 2010).

South Africa is a signatory to the Kyoto Protocol and the Paris Agreement and has agreed

through the adoption of its National Climate Change Response Policy in 2011 to implement

mitigation measures (reducing greenhouse gas emissions) and adaptation measures (ensuring

climate-change resilience through public investments) to reduce greenhouse gas emissions by

34 % in 2020 and 42 % in 2025, subject to certain conditions (NT 2014).

The implementation of carbon tax is an important component of this mitigation policy.

National Treasury published the Draft Carbon Tax Bill for comment in November 2015 with the

intention that carbon taxes would be implemented in a phased manner with effect from

1 January 2017 (NT 2014, NT 2015, Martineau 2017). The purpose of the 2015 Draft Carbon

Tax Bill is to address climate change and to facilitate a viable transition to a low-carbon

economy by combating GHG emissions, but also taking advantage of new investment

opportunities (NT 2015).

An analysis of mitigation potential by the Department of National Treasury shows that the

following focus areas could be eligible for projects (NT 2014):

Energy and energy efficiency with reference to energy efficiency in

household and commercial sectors, small-scale renewable energy, community-

based and municipal energy efficiency, renewable energy fuel-switching

projects and electricity transmission and distribution efficiency.


66

Agriculture, forestry and other land uses with specific reference to anaerobic

biogas digesters.

Waste management with reference to municipal waste.

Biogas schemes are also entitled to Clean Development Mechanism (CDM) rebates as they

remove methane production from the atmosphere; especially taking into account that

methane is up to 30 times more effective as a greenhouse gas than carbon dioxide (Ruffini

2014, Atkins 2017). CDM mechanisms are evolving continuously, also allowing the pooling

of a number of small projects to gain credits - a model that is very suitable to biogas

digestion.

It is estimated that the average reduction in emissions that could be realised between 2013

and 2032 from the CDM projects registered as of November 2012 equals 17.2 million tonnes

CO2 per year as shown in Table 2 addressing the following sectors: biogas, biomass, energy

efficiency, fuel switch, methane recovery and utilisation and waste gas/heat recovery (Camco

Clean Energy 2012, NT 2014).

Table 2: CDM credits expected to be issued in South Africa per project type. (Source NT

2014)

Sector Certified Emission

Reduction (CERs)

Biogas 103 672

Biomass 881 144

Energy efficiency 398 098

Fuel switch 1 662 205

Hydro power 169 693

Methane recovery and utilisation 1 694 461

N2O decomposition 2 164 037

Waste gas/heat recovery 1 945 559

Wind 7 561 841

Solar photovoltaic 473 624

Concentrated solar power (CSP) 230 537

Total 17 284 871

Tiepelt (2017) believes that the carbon mitigation potential of the biogas industry gives

export companies a competitive advantage in overseas markets where the carbon footprint of

the company is required. GreenCape (2017a) however states that currently no official

sustainability accreditation exists, and that investors are not necessarily motivated by the

potential of the development to contribute to sustainability but are rather driven by the

purpose of the project be it electricity generation or waste management. Atkins (2017)


67

confirmed that tax incentives would not exist in South Africa until the carbon tax is indeed

implemented.

4.4 Efficient waste management

While SAGEN and SABIA (2016) reports that currently the South African biogas industry is

mainly used to solve waste management problems by redirecting solid and hazardous waste

away from landfills, biogas generation also presents an alternative renewable energy resource

especially in rural areas as it can be located wherever waste feedstock is available, making it

particularly suitable for rural areas (Amigun et al. 2012).

Potgieter (2011) referred to the potential of biomass as renewable energy resource as the

combined energy value of all the various biomass types available that can realistically be

converted into bioenergy, and found that the potential of biomass as renewable energy

resource exceeds the annual primary energy consumption of the world. Other investigations

into the available waste streams show that there is potential to implement many more

anaerobic digesters nationwide, particularly as a cost-saving measure where waste can be

diverted from landfills or re-used as a source of heat or energy (Barnard and Holzbaur 2013,

GreenCape 2017b, GreenCape 2017c).

Government rebate programmes are in place as part of the Waste Management Flagship

Programme (WMFP) and states that “the Department of Environmental Affairs will

determine the GHG mitigation potential of the waste sector and investigate the opportunities

for waste-to-energy conversion practices, as well as the production and capture of methane

or landfill gas from waste sites. This information will be used to develop and implement a

detailed waste-related GHG emission mitigation action plan, and detail appropriate policies

for facilitating its implementation” (NT 2013). While internationally government-initiated

programmes supports the use of many more feedstock avenues on a large scale, there is still

much potential for such government-initiated programmes in South Africa (SAGEN and

SABIA 2016).

Green fuels are well developed in Sweden and India, where many taxis are already running

with the use of gas bottles, while relatively undeveloped in South Africa (Biogas 2013).

According to Raoul Goosen (Industrial Development Corporation’s Green Industries

Business Unit), vehicular biogas also provides an important waste management opportunity

since one tonne of bio-waste is equal to the equivalent of 1 000 litres of petrol and 1 000 km


68

of CO2 neutral drive (3SMedia 2013). GreenCape (2017a) believes that the growth in duel

fuel transportation systems will further stimulate the biogas market.

4.5 Utilisation of digestate as organic fertiliser

There is sufficient scientific and practical evidence of the capability of digestate to act as a

soil conditioner and to enhance plant growth and yields (Dennis and Burke 2001, Dillon

2011, Torquati et al. 2014, Msibi 2015, SAGEN and SABIA 2016, Culhane 2017,

GreenCape 2017a, Tiepelt 2017). South Africa is a net importer of fertilisers, importing all its

potassium, as well as 60 % to 70 % of its nitrogen requirements (Figure 1).

Figure 1: Fertiliser imports and exports per annum in South Africa from 2014 to 2017

(Source: FERTASA 2017). This information is regularly updated by the Fertiliser

Association of South Africa (FERTASA), thus the tonnage for 2017 is valid for the date that

it was sourced; 2nd October 2017).

In this deregulated market environment, fertiliser prices are strongly influenced by

international prices, currency exchange rates (ZAR/USD) and shipping costs (DAFF 2015).

The use of digestate as potential supplement for specific mineral nutrients provides economic

and environmental advantages. Guatam et al. (2009) found an annual savings of 4 329 T N,

2 109 T of phosphorus and 4 329 kg potassium due to the installation of biogas digesters in

Nepal that replaced previously imported chemical fertilisers with the organic form of

digestate fertilisers. An additional major benefit is that the digestate produced from a biogas


69

digester can be considered as an organic fertiliser rendering it suitable for soil improving

(Makádi et al. 2012, Tiepelt 2017). By contributing to the direct carbon sequestration through

the use of organic material sourced from the digested matter, carbon can also be directly

sequestered in the soil (De Neve et al. 2003). The increased application of organic matter

reduces erosion and stabilises sandy soils further improving water quality (Yongabi et al.

2009).

However, GreenCape (2017c) found that in South Africa a difficulty in finding offtakers for

digestate exists and that mechanisms are needed to concentrate the digestate and reduce the

volume, which links to lower logistic and handling costs.

Figure 2: Fertiliser consumption of nitrogen (N), phosphorus (P) and potassium (K) in South

Africa per annum from 2005 to 2015 (Source: DAFF 2016)

4.6 Job creation

Probably the most important consideration when promoting the biogas industry is its potential

to create jobs (SAGEN and SABIA 2016). A recent study on opportunities for job creation in

renewables compared the government’s current pathway based on the 2011 Integrated

Resource Plan for electricity (IRP), to the Green Peace Advanced Energy Revolution

(GPAER). The IRP will result in 111 000 direct jobs by 2030, compared to 149 000 direct

jobs in the GPAER (GreenPeace 2011). Ruffini (2014) estimated that biogas as a renewable

energy source could lead to five times more permanent job opportunities than what is


70

available in solar energy. GreenCape (2017c) estimated that based on its potential, job

creation is estimated at 320 to 3950 direct jobs, at a job intensity of 4 – 10 jobs per megawatt

(MW) of installed electrical capacity.

5.0 Challenges and enablers of the South African biogas digester industry

Obtaining renewable energy through biogas generation could be particularly complex,

(Torquati et al. 2014). GreenCape (2017a) believes that the many variables in the South

African scenario complicates implementation as there is no single solution applicable to most

as is often found to be the case in Europe, and that implementation here should be site-

specific to succeed. Lack of government involvement and motivation to support biogas

production is a drawback for the industry (GreenCape 2017c) and Tiepelt (2017) argues that

the biogas industry cannot establish itself in any country in the world without a source of

subsidy.

Challenges in South Africa do not lie in the development of the biogas digesters but

translational research is needed to make it possible for digesters to be locally produced, and

implemented in an effective, safe and affordable way with specific reference to South African

circumstances (Terreblanche 2002, Woolard and Leibbrandt cited in FAO 2004, Smith 2011,

Ruffini 2014, GreenCape 2017a, GreenCape 2017b).

5.1 Lack of awareness

Enabler: While current lack of awareness of biogas digesters in the public sector, private

sector and government curbs the potential of the industry, an enabling factor in this regard is

the contribution of SABIA, industry stakeholders and industry to create increased

understanding of the potential of the industry (AltGen, GIZ, SAGEN and GreenCape 2014,

SAGEN and SABIA 2016, Tiepelt 2017).

5.2 Regulatory and time constraints

A full environmental impact assessment (EIA) is required for the establishment of all plants

that produce methane (AltGen, GIZ, SAGEN and GreenCape 2014, GIZ-SAGEN 2015,

SAGEN and SABIA 2016, Tiepelt 2017). To fulfil these environmental licensing

requirements are time consuming and not cost effective (GIZ-SAGEN 2015, Tiepelt 2017).


71

Tiepelt (2017) regards the amount of time spent to implement endeavours is a major

challenge in South Africa. The Bronkhorstspruit project took about seven years from

initialising the project, to the start of the building process, and another 18 months to build the

plant (Bio2Watt.com 2017).

In addition, long-term supply contracts for waste facilities pose a problem as most waste-to-

energy facilities have a payback period of 15-20 years, and, to attract investors, could require

contracts of the same length for the feedstock. This has proven challenging for South African

companies that target municipal solid waste as municipalities typically have three to five-year

procurement contracts (GreenCape 2016, Tiepelt 2017).

Enabler:

Streamlining EIA processes and making provision for requiring less licencing for

plants with lower output could enable the development of the industry (GIZ-SAGEN

2015).

5.3 Electricity wheeling arrangements and supply

Another major factor in curbing the advancement of the industry is the wheeling agreement

between the power generator and the owner of the grid – either Eskom or the local

municipality (GreenCape 2017c, Tiepelt 2017). In the case of the Bronkhorstspruit project,

power had to be wheeled from Bronkhorstspruit, through the Eskom grid, to the Tshwane

grid, and then from the Tshwane municipality to the BMW site in Rosslyn Pretoria which

acts as the off-taker of the electricity.

In terms of electricity supply and demand, farmers in South Africa are faced with the

challenge of excess electricity (Tiepelt 2017). In Europe, farmers may generate electricity

24/7, and after using what they require, supply the excess electricity to the national electricity

grid. In South Africa, however, excess energy cannot be fed to the national electricity grid,

which means that a farmer has to be able to use 90 % of the electricity generated to make his

project viable and financially sound (Tiepelt 2017). GreenCape (2016) adds that further

constraints include the lack of feed-in tariffs for renewable energy outside of the REIPPPP

(which only applies to projects larger than 5 MW) as well as the lack of a policy/regulatory

framework for grid connection by independent power producers outside of the REIPPPP.


72

In addition, electricity prices as compared to developed countries are still low (although the

cost of electricity is escalating quickly), and waste-to-energy is still proving to be more

expensive (R1.40-R1.60 /kWh) compared to bulk electricity prices (R0.50-R0.90 /kWh more

on average) (GreenCape 2016, GreenCape 2017a). GreenCape (2017c) found that although

the intent of the REIPPPP was to encourage waste-to-energy projects as well, no biogas

projects have been successful in the various bidding rounds for utility scale renewables.

Taking this into account GreenCape (2017a) believes that at this stage it does not pay biogas

plants to feed electricity into the grid, and that electricity generated should be used on site or

sold at a premium.

Enablers:

Small-scale embedded generation (SSEG) tariffs would enable biogas facilities to supply

electricity generated through wheeling operations, where the electricity is not sold to Eskom

or the Municipality but through a power purchase agreement with a business entity.

Frameworks for wheeling arrangements are under development at certain municipalities

(GreenCape 2017a).

Exemption from electricity generation licences are expected to be Gazetted soon

which will enable generation for own use on site, for back-up storage, for pilot

projects, for off-grid use and for wheeling for single use without requiring a licence

(GreenCape 2017a).

GreenCape (2017a) foresees that municipalities will in the near future be able to buy

electricity from any independent power producer and not only Eskom, awaiting

government approval. Creating a market for surplus energy generated by plant with a

capacity of <1MW, could enhance the potential of the biogas industry (AltGen, GIZ,

SAGEN and GreenCape 2014, SAGEN and SABIA 2016, Tiepelt 2017).

Electricity trading will enable third party traders to buy excess energy from Eskom or

municipalities and sell it to clients. This will assist municipalities who have reached

their demand (GreenCape 2017a).

5.4 Financial requirements

Karekezi (2002) noted that practical problems in biogas project developments include

unaffordable initial investment costs. Tiepelt (2017) together with GreenCape (2017c) argues


73

that financial viability remains the biggest test to the South African biogas industry.

GreenCape (2017c) stated that overall in the South African context, financial viability of

biogas projects is highly site-specific and only strong under certain conditions. GreenCape

(2017c) further states that failure of projects in South Africa has primarily been due to

unfavourable cost-benefit ratio, often as a result of insufficient scale, and particularly when

electricity generation was not utilised, or could not be utilised as envisioned (e.g. fed into the

grid). SAGEN and SABIA 2016 states that high capital costs and lack of remuneration

mechanisms for electricity generation <1 MW as a hindrance. This is sustained by GreenCape

(2016) identifying the lack of feed-in tariffs for renewable energy outside of the REIPPPP,

which only applies to projects larger than 5 MW as a challenge. Current tight capital margins

further inhibit the industry to appoint and remunerate qualified plant operators (AltGen, GIZ,

SAGEN and GreenCape 2014, SAGEN and SABIA 2016, GreenCape 2017c, Tiepelt 2017).

Taking the current Eskom tariff together with the escalation of the Eskom tariff over the next

five years into account, biogas plants may only break even after approximately 4-5 years, and

start to pay back after 7-10 years, making it not readily viable on a farm-scale if the

motivation to implement biogas digesters is primarily based on a pay-back return point

(GreenCape 2016, Tiepelt 2017).

The Department of Trade and Industry (DTI) have an incentive programme MCEP

(Manufacturing Competitive Enhancement Project) (ESI-AFRICA 2016), which farmers can

apply for, but it has been over-subscribed, making it currently inaccessible for farmers (DTI

2015, Creamer 2016, Tiepelt 2017). All new applications for the MCEP were suspended in

October 2015, reportedly necessitated by a lack of funds as the more than R5 billion set aside

for this programme was fully committed (DTI 2015). According to Creamer (2016), the new

application window was set to open in April 2016 but is delayed due to inadequate funding.

While the agriculture sector implored the DTI to continue with the MCEP, full reactivation will

only happen once adequate funding is secured (Creamer 2016).

Enablers:

The opportunity that it presents to larger corporate industries in terms of expanding

green footprint production and carbon mitigation incentives, could make it financially

more viable for such institutions (SAGEN and SABIA 2016, GreenCape 2016,

GreenCape 2017c, Tiepelt 2017).


74

ESI-AFRICA (2016) reports that there are incentives to overcome limited funding for

small projects such as the Manufacturing Competitiveness Enhancement Programme

(MCEP), Eskom’s Industrial Demand Side Management (IDM), the Industrial

Development Corporation’s Green Energy Efficiency Fund, as well as foreign

funding and a gradual involvement by local banks to participate in long-term biogas

financing.

Increasing waste management costs (GreenCape 2017c)

Private-public partnerships have proved to work well in other parts of the world such

as in Thailand, Nepal, India and Germany (Biogas 2013).

More streamlined processes could potentially require less capital investments

(AltGen, GIZ, SAGEN and GreenCape 2014, SAGEN and SABIA 2016, Tiepelt

2017).

5.5 Scale of projects

The scale of the biogas project or plant also has an impact on its potential for success. Two of

biggest current participants in biogas generation are 5.5.1 municipalities and 5.5.2 farmers

(Biogas 2013, Mutungwazi et al. 2017, Tiepelt 2017).

5.5.1 Municipalities

Municipalities are challenged by the time span of the projects. Biogas generation projects in

South Africa have a long payback period of approximately 10 to 15 years (AltGen, GIZ,

SAGEN and GreenCape 2014, SAGEN and SABIA 2016, Tiepelt 2017). Municipalities are

bound by the MFMA (Municipal Financing Management Act), which only allows them to

sign a contract for three years, and for longer periods they need to acquire approval from the

National Treasury of South Africa (NT-MFMA 2017). This is thus found to be a hindrance

because of the lingering tender process combined with the unstable economic state of the

government of South Africa (Peyper 2017, Tiepelt 2017).

5.5.2 Farmers

Tiepelt (2017) regards farmers as another major potential participant/client, especially dairy

farmers and housed dairy farmers. In terms of financing a project on this scale, there are two

major primary requirements. The first major requirement is a signed agreement for feedstock,

and secondly, a signed agreement for energy off-take. GreenCape (2016) supports this by


75

listing availability of sufficient feedstock and the lack of feed-in tariffs for renewable energy

outside of the REIPPPP, which only applies to projects larger than 5 MW as a challenge.

GreenCape (2016) also states that the biggest opportunity for biogas production in South

Africa is in the accumulated benefits of multiple small-scale plants on farms but that farmers

are often negatively affected by the challenges of the industry such as perceived financial

losses and skills shortages (GreenCape 2017a, GreenCape 2017c).

Enablers:

Better negotiation of contract agreements, especially taking into account that biogas

facilities differ dramatically from farm to farm and are influenced by the merits of

each situation (GreenCape 2017a).

Ensuring consistent feedstock supply and consistent off-take will enable more

efficient and cost-effective operations (GreenCape 2017a).

Increased trust in developers and the validity of their products as well as better

product warranties could increase interest in new technologies (GreenCape 2017a,

GreenCape 2017c, Steyn 2017).

GreenCape (2017a) has established an agriculture portal managed by their agriculture

desk to inform the farming community about sustainable agriculture practices such as

biogas generation.

5.6 Skills shortage and development

A particular hindrance in South Africa is the major skills gap due to the lack of available and

qualified biogas skills development avenues and restricted access to biogas specific

education, both locally and internationally (SAGEN and SABIA 2016, GreenCape 2017c).

Mutungwazi et al. (2017) found that the failure of biogas digesters could be ascribed to the

suitability and availability of the materials used, poor building skills and lack of knowledge

regarding system design and operation. Tiepelt (2017) confirmed that South Africa lacks the

experience of operating biogas plants that is needed to optimise the country’s biogas

potential. GreenCape (2017c) stated that insufficient knowledge and skills training has

resulted in several costly process issues. With developers currently being the only party

investing in mostly in-house skills training, there exists little potential for cross-pollination of

skills from outside of the industry. SAGEN and SABIA (2016) predicts that this skills gap


76

will expand with the growing market should there be no intervention and standardisation of

technical skills.

Enablers:

Creating opportunities to train skilled or semi-skilled employees in the biogas sector,

may resolve in cheaper labour cost for better and consistent qualified labour (SAGEN

and SABIA 2016, Tiepelt 2017).

The South African Renewable Energy Technology Centre (SARETEC) is the first

national renewable energy technology centre of its kind in the country, located at the

Cape Peninsula University of Technology (CPUT). SARETEC promotes specific

industry-related and accredited training for the renewable energy industry including

short courses and workshops (SARETEC 2017). GreenCape (2017a) believes that

SARETEC could assist in skill training.

5.7 Ethical challenges

The use of sewage sludge as a soil conditioner presents a psychological and ethical challenge.

Walekhwa et al. (2009) described this as a socio-economic factor that can influence the

uptake of biogas digesters projects. Possible negative impacts on the development of the

industry are the potential for pathogens present in the digester slurry to contaminate the

people who handle it or eat crops fertilized with it (DA, DH, DAFF, WISA and WRC 1997,

Brown 2006, Yongabi et al. 2009). Rabezandrina (1990) and Amigun and Von Blottnitz

(2009) also noted as hindrances the potential to pollute water souces through leakages from

faulty digesters or from runoff of undigested material that has been applied to soils. However,

this is contradicted by studies that maintain that biogas destroys pathogens through the

thermophilic AD, meeting the requirements of the hygienic indicators of the European Union

(Paavola and Rintala 2008).

Enablers:

Using the digestate as a soil enhancer and for soil preparation presents no problems

when the digestate does not come into direct contact with the edible parts of the

produce (Paavola and Rintala 2008). In the past in South Africa, farmers have used

the sludge of wastewater treatment works as a source of soil conditioner/enhancer in

soil preparation (DA, DH, DAFF, WISA and WRC 1997). Tiepelt (2017) further


77

confirms that sewage sludge is still being used in this sense in South Africa, showing

a change in acceptance of alternative sources of fertilisers (Tiepelt 2017).

5.8 Water resources

South Africa is a water-scarce country (OXFAM 2016). This presents challenges for the

biogas digester industry and especially for smaller scale digesters as anaerobic digesters

require a lot of water to function (Swanepoel 2014).

Enablers:

Tiepelt (2017) believes that this should not restrict the growth of the industry as large

volumes of the liquid digestate can be recirculated and used for further dilution. While

this cannot be done indefinitely; up to 80 % of the liquid can be reused depending of

the type of feedstock, reducing the water requirements of a digester substantially

(Morales-Polo and del Mar Cledera-Castro 2016, Bansalet et al. 2017).

Reutilising the liquid digestate also has its benefits as the temperature of reused

digestate is higher and the warmer water creates a more suitable micro habitat for

digestion (Morales-Polo and del Mar Cledera-Castro 2016, Bansalet et al. 2017,

Tiepelt 2017).

5.9 Access to and segregation of waste

As many thermal waste-to-energy technologies need large-scale facilities to be viable and

achieve economy of scale (e.g. 1 000-2 000 T/day), access to sufficient feedstocks can be a

challenge (GreenCape 2016, GreenCape 2017a, GreenCape 2017c). Low gate fees at landfill

sites also make it difficult for other technologies to compete with landfilling as the cheaper

alternative (GreenCape 2016, GreenCape 2017b). Current waste laws (NEM:WA) prevents

abattoir waste to be treated with municipal wastewater or sent to landfills which enable the

use of anaerobic digestion to dispose abattoir waste.

Transparencymarketresearch (2017) states the overall lack of effort going into the separation

of wastes before disposal as a global hindrance that can negatively affect developing

countries. There is a major absence of implementation of processes meant to sort waste,

which is the basic requirement for any waste type to be reused or recycled. While the global

biogas plant market is in a very good position to increase its output volumes and


78

infrastructure, it is particularly held up by this lack of waste segregation policies and systems,

especially in emerging economies around the world.

Interventions with the aim to divert 100 % of organic waste from landfills may result in less

organic waste being available for biogas generation (GreenCape 2017a). A challenge faced in

fertiliser production is the inconsistent control of minerals included in the digestate as the

composition of digestate differs as feedstock types differ. This is especially true regarding

municipal solid waste as the feedstock often consists of random portions of waste resulting in

inconsistent output. The unintentional inclusion of foreign objects or toxic substances in

waste could lead to health issues or financial losses (GreenCape 2017b, GreenCape 2017c).

In addition, competition for wet food waste is very high between pig farmers, fly farmers,

compost companies and biogas producers, especially waste solutions that may be more

financially feasible (GreenCape 2017a).

Enablers:

Stricter licencing requirements for the diversion of organic waste from landfills could

mean that alternative solutions for organic waste such as biogas generation are

explored (GreenCape 2017a).

Biogas generation creates waste disposal solutions for companies reducing waste

transport costs and the costs of generation heat and electricity (GreenCape 2017a).

Streamlining biogas generation legislation could act as an enabler in this regard

(AltGen, GIZ, SAGEN and GreenCape 2014, SAGEN and SABIA 2016, Tiepelt

2017).

Results and discussion

Biogas generation has a long history in South Africa, with its initial application limited to

treat sludge in wastewater plants. The growing interest in biogas generation in recent years

can be attributed to its potential to provide solutions for the continued challenges faced in

terms of energy generation and waste management (GreenCape 2017a, GreenCape 2017c,

Tiepelt 2017).

Biogas generation could potentially contribute to the alleviation of poverty and the

improvement of the well-being of communities, by integrating waste management and

renewable energy technologies (Biogas 2013, DEA 2013, SAGEN and SABIA 2016,


79

GreenCape 2017a). In this way it presents a unique opportunity to impact all three pillars of

sustainability in a developing country like South Africa.

Biogas generation as an alternative renewable source of energy could potentially mitigate the

effects of climate change and enable the country to meet peak electricity demands as it is not

dependant on resources like wind or water and can be implemented on any site where waste

feedstock is readily available. This also makes it a suitable option for small or farm-scale

application as rural wastes are mostly organic and biogas energy generation can provide

options to save on electricity bills and provide innovative solutions to waste management

problems (SAGEN and SABIA 2016) while the digestate has the potential to be repurposed

as organic fertiliser. In addition numerous ecosystem services are rendered that could

ultimately increase food production (NERSA 2013, Ji-Quin and Nyns 1996), again linking

the benefits of biogas generation to the Sustainable Development Goals of the United Nations

(UNDP 2017).

While South Africa’s sustainable development policies commit the country to a sustainable

development path (DEA 2008, DEA 2013, DEA 2016) the slow development of anaerobic

digestion, both on a commercial and rural scale, as compared to other developed and

developing countries, could be due to numerous challenges such a lack of awareness of the

industry, a lack of government support, intensive capital investment requirements, slow and

hindering legal processes, a skills shortage, ethical challenges and the complicated nature of

electricity supply and demand.

Enablers could however contribute to the growth of the industry and include skills training,

increased trust and safeguards in the products installed, streamlining of legislation pertaining

to licencing, carbon incentives and waste, and joint ventures between the public and private

sector to alleviate financial constraints. Exemption from electricity licences, the proposed

SSEG tariffs and new frameworks for wheeling arrangements will increase the opportunities

to feed excess electricity into the grid or sell it to clients directly (GreenCape 2017a, Scharfy

et al. 2017).

What counts in favour of the development of this industry is the perceived tenacity of project

developers that continue to pursue the development and marketing of such systems even in a

situation where there is limited awareness and knowledge about biogas generation (Tiepelt

2017). They are supported in their endeavours by the contribution of the South African

Biogas Association and various industry stakeholders such as GreenCape.


80

Conclusion

With the acknowledgement of the critical importance of moving towards more sustainable

development in South Africa, and taking into account South Africa’s vision for sustainability,

the use of anaerobic digestion for the generation of electricity and efficient waste

management has great potential to contribute significantly to sustainable development. This is

measured against the growth in the biogas generation industry seen over the last decade, even

in the face of numerous challenges such a skill shortages, lack of financial incentives,

financial constraints, ethical issues, limited water resources and policy and legal

requirements.

Biogas generation has the potential to contribute to a more sustainable farming approach

through the production of energy and thermal heat to be used on site, reduction in electricity

costs, providing waste management solutions and the production of organic fertiliser for own

use or as an additional source of income.

In the rural sector the generation of electricity and gas could not only contribute to local

economic development but also to the quality of the lives of people through the use of an

alternative energy source to enhance the quality of their lives.

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Presentations

SAIREC. (2015) Biogas in South Africa. South African International Renewable Energy

Conference (SAREC). 4 – 7 October, Cape Town. Presented by: Mark Tiepelt

AltGen, GIZ, SAGEN and GreenCape. (2014) An Estimation of the Job Potential and









http://www.bio2watt.com/

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PAPER 2: EVALUATING THE POTENTIAL OF ON-

FARM BIOGAS GENERATION AS A SUSTAINABLE

AGRICULTURAL PRACTICE THROUGH INTER-

ACTION WITH THE FARMING COMMUNITY

Abstract

The rationale of this study was to establish the potential of farm-scale biogas generation as a

sustainable agricultural practice in South Africa. Findings are based on interaction with two

groups of farmers – 1) those without biogas digesters and 2) those with biogas digesters.

Purposive data collection was conducted through two self-administered electronic surveys

that were sent to farmers of both these groups. Farmers in the Western Cape, KwaZulu-Natal,

Mpumalanga, Northern Cape, Free State and Gauteng were included in the surveys, covering

agricultural practices such as animal husbandry, agronomic crops, fruit and aquaculture.

Information obtained was further supported and clarified through personal conversations with

participants in both surveys and measured against what is defined in this paper as

sustainability, economic potential, social potential and environmental potential – the three so-

called pillars of sustainability. It was found that, although substantial understanding of

sustainability, effects of climatic change and the economic potential of biogas generation

exists, a lack of knowledge, expertise, financial support and incentives remains an obstacle in

the practical implementation of biogas generation and the potential it shows to provide a cost-

effective renewable source of energy to enhance the quality of life in rural areas.

1.0 Introduction

1.1. Biogas production as a sustainable agricultural practice

Sustainability is an important concept in this study, as the potential to generate biogas as a

sustainable agricultural practice is evaluated against the impact it may have on the three

pillars of sustainability namely economic, social and environmental.

In this paper sustainability is defined as: “The process of utilising and living within the limits

of available physical, natural and social resources in ways that promote social, ecological

and economic sustainability all at the same time, while allowing the living systems in which


93

humans are entrenched to flourish in perpetuity” (UN 1987, DEA 2008, Kuhlman and

Farrington 2010, Morelli 2011, EPI 2014, Uwosh.edu 2017).

The agriculture sector in South Africa shows great sustainable potential for biogas

implementation on small to medium farm scale (Smith 2011, Biogas 2013, Hamilton 2014,

Shah et al. 2015, Zafar 2015, GreenCape 2016, GreenCape 2017a, Tiepelt 2017).

South Africa was one of the first countries in the world to utilise biogas on a pig farm south

of Johannesburg in the early 1950s (GIZ-SALGA 2015), with the two biggest participants in

biogas generation today being identified as municipalities and farmers – especially dairy

farmers and housed dairy farmers (GreenCape 2016, GreenCape 2017a, Tiepelt 2017).

Not only could farm-scale biogas generation stimulate the much-desired rural renewal,

improve long-term sustainability of ecosystem services and address energy poverty in South

Africa; the biggest opportunity for biogas production lies in the accumulated benefits like

many decentralised small-scale plants on farms (Mshandete and Parawira 2009, Smith 2011,

Amigun et al. 2012, NERSA 2013, GreenCape 2016). Farms could benefit through the

generation of electricity, waste treatment, storage and transportation and fertiliser production,

especially as energy has been identified as a major element in the competitiveness and

sustainability of the farming sector (Mshandete and Parawira 2009, Smith 2011, Abbasi

2012, Biogas 2013, Griffiths 2013, NERSA 2013, Carter and Gulati 2014, SAGEN and

SABIA 2016, GreenCape 2017a, Tiepelt 2017). Lutge (2010) found that as far as the

economic potential of on-farm electricity generation through biogas is concerned, each farm

should be treated as an independent unit. This supports the notion to direct surveys to

individual farmers, those who do not make use of biodigestion, as well as those who do, in an

effort to establish whether any common denominators exist that could influence their

decisions.

Previous studies analysed the biogas potential of wastewater treatment plants (GIZGmbH

2016) and the potential for domestic biogas as household energy supply (Msibi and Kornelius

2017), as well as the potential of producing biofuels as a new technology to overcome food

security and resource issues (Amigun et al. 2011). Kumba et al. (2017) investigated the

design and sustainability of a biogas plant for domestic use. No surveys directed to individual

farmers to assess the on-site agricultural potential of biogas generation have been known to

be published so far. Msibi and Kornelius (2017) found that based on livestock numbers,

some 625 000 South African households could benefit from biogas generation based on cattle


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and pig waste, but that it is not feasible to run a domestic bio-digester on only human,

chicken and food waste because of inadequate feedstock. Amigun et al. (2011) concluded

that biofuels, in themselves, pose few sustainability risks for food production in terms of land

and water resources and that its conservative application could enhance the productivity of

the agricultural system. Kumba et al. (2017) studied design parameters for biogas digesters

through field surveys and concluded that the organic loading rate, hydraulic retention time

and feedstock play a major role in determining the design of such systems.

The willingness or non-willingness of participants, and those who were approached to

participate in this study, gave further insight into the potential of biogas generation in the

agricultural sector as it highlighted the limitations set on the industry through perceptions and

frustrations experienced. The scepticism encountered is supported by Amigun et al. (2011)

who have pointed out that some small-scale farmers are sceptical of new ventures and

generally are not willing to engage in farming activities that they are not familiar with.

The study expects to gain insight into the understanding, knowledge, experience and

awareness of sustainability, climate change and implementation of biogas digesters on farm

scale, as well as to identify major challenges faced by these farmers, hindering the process of

unlocking of the sustainable potential of biogas generation on farm scale in South Africa.

1.1.1 The economic potential of biogas production as a sustainable agricultural practice

Energy is a driver of economic growth and it is estimated that biogas generation could supply

about 6 % of the global primary energy demand, or one quarter of the present consumption of

natural gas (Holm-Nielsen et al. 2007, World Economic Forum 2012). Energy is also

regarded a major element in the competitiveness and sustainability of the farming sector, and

that is why anaerobic digestion is seen to have the highest potential to be implemented on

farms that as a potential solution to South Africa’s ever-present electricity crisis, and the

resultant trends of unsustainable consumption and production (Smith 2011, Amigun et al.

2012, Griffiths 2013, Carter and Gulati 2014, SAAEA 2016, SAGEN and SABIA 2016,

Teljeur et al. 2016, Tiepelt 2017).

For the purpose of this paper, economic potential is defined as “the available technical

potential in terms of biogas generation, where the cost required to generate the energy

(which determines the minimum revenue requirements for development of the resource) is


95

below the revenue available in terms of displaced energy and displaced capacity” (Brown et

al. 2016).

It is maintained that economic potential can be realised in the agricultural sector for the

following reasons:

1.1.1.1 The potential to supply in energy/heat demands by making use of the availability of

feedstock

Anaerobic digestion (AD) produces biogas when organic matter, such as plant material,

animals and their wastes and waste water, decay through a natural anaerobic bacterial

process, offering the possibility to regionalise energy delivery (Dennis and Burke 2001,

Arbon 2005, Amigun et al. 2012, Biogas 2013, Shah et al. 2014, GreenCape 2017a).

GreenCape 2016 estimated that the total electricity potentially generated from biogas in

South Africa from agricultural waste is 2 300 MWe (MegaWatt electric), and Abbasi (2012)

predicted that by 2020 the largest volume of produced biogas will come from farms and large

co-digestion biogas plants that are incorporated into farming and food-processing structures.

1.1.1.2 The potential to produce organic fertiliser that can be used as soil conditioners or

compost

There is sufficient scientific and practical evidence of the capability of digestate to act as a

soil conditioner and to enhance plant growth and yields, especially taking into account that

nearly 80 % of South African land is agricultural land with an estimated fertliser use of 60,6

kilograms per hectare of arable land (Dennis and Burke 2001, Tambone et al. 2007, Schleiss

and Barth 2008, Tambone et al. 2009, Dillon 2011, Makádi et al. 2012, Torquati et al. 2014,

Msibi 2015, SAGEN and SABIA 2016, Culhane 2017, GreenCape 2017a, Tiepelt 2017,

Tradingeconomics.com 2017). Biogas generation on farm scale could provide a mechanism

to reuse waste for soil conditioning and to save on fertiliser costs, as the digestate could be

used as a treated soil conditioner on site or supplied to agricultural fertiliser producers

(GreenCape 2016, Tiepelt 2017).

1.1.1.3 The potential to find affordable financial solutions to the challenges of operational

costs and revenue possibilities


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Substantial capital costs make the return on investment into a biogas plant for a farmer that

has access to a reasonable amount of organic waste, directly dependent on the replacement

cost of Eskom-bought electricity (BiogasSA 2017). However, long payback periods, limited

electricity generation potential and the lack of feed-in tariffs for renewable energy outside of

the Renewable Energy Independent Power Producer Procurement Programme (REIPPPP),

makes it a risky and unattractive investment for the average farmer in South Africa

(GreenCape 2017c, BiogasSA 2017). Numerous incentives are however underway that could

make biogas generation on farm-scale more viable including better negotiation of contract

agreements, especially considering the merits of each situation; ensuring consistent feedstock

supply and consistent off-take; using both heat and electricity generated on site; and selling

electricity generated at a premium through newly-negotiated power purchase and wheeling

agreements with municipalities (GreenCape 2017a).

1.1.1.4 The potential of accessing realistically available governmental support

Incentives and rebates could make farm-scale biogas plants a lucrative option for farmers

looking to reduce their carbon footprint and save on electricity bills (Biogas 2013, Griffiths

2013). However, the effective implementation and allocation of funds regarding these

incentives are found to hinder the potential of biogas generation development in South Africa

(AltGen, GIZ, SAGEN and GreenCape 2014, DTI 2015, Creamer 2016, ESI-AFRICA 2016,

GreenCape 2016, Tiepelt 2017). Future enabling factors could include exemption from

electricity generation licences; the potential to sell electricity to a third party through power

purchase agreements; the fact that municipalities could possibly buy electricity from any

independent power producer and not only from Eskom; and creating a market for surplus

energy generated by plant with a capacity of <1MW (AltGen, GIZ, SAGEN and GreenCape

2014, SAGEN and SABIA 2016, Tiepelt 2017). It could also provide tax relief through the

anticipated implementation of carbon tax; promote solutions for waste management and the

organic fertiliser industry, while delivering ecosystem services such as carbon sequestration

in soils and improved water and soil quality and, ultimately, an increase in food production

(Onwosi and Okereke 2009, Mtambanengwe and Mapfumo 2005, Fonte et al. 2009).


97

1.1.2 The social potential of biogas production as a sustainable agricultural practice

As agricultural activities directly affect the social life and well-being of communities, it can

be seen as maintaining social viability in rural communities (OECD 2000). In the same way,

biogas generation is linked to the Millennium Development Goals of reducing income

poverty, promoting gender quality, promoting health and environmental sustainability (UN

2015). Farm-scale biogas digesters have great potential to contribute to sustainable

development by providing a secure energy supply, enhanced regional and rural development

and employment opportunities, and the creation of a domestic industry (Rio and Burguillo

2008, Mshandete and Parawira 2009, NERSA 2013).

For the purpose of this paper, social potential refers to “Identifying and evaluating the social

issues and related indicators that can enhance social conditions in South Africa related to

sustainable development of biogas generating facilities”.

It is maintained that social potential can be realised in the agricultural sector for the following

reasons:

1.1.2.1 The potential to create jobs and opportunities for skills transfer and education

Probably the most important consideration when promoting the South Africa biogas industry

is its potential to generate five times more permanent job opportunities than solar energy

(Ruffini 2014, SAGEN and SABIA 2016). As a lack of skills for the operation and

functioning of a biogas plant on farm-scale is seen as a challenge (Tiepelt 2017), initiatives

such as the agricultural portal on sustainable agriculture at GreenCape that creates training

opportunities to skilled or semi-skilled employees through The South African Renewable

Energy Technology Centre (SARETEC), opens the opportunity to build knowledge, skills

and experience (GreenCape 2017a) especially in the agricultural sector.

1.1.2.2 The potential to deliver health benefits and improve the standard of living

It is estimated that half a billion people in sub-Saharan Africa rely on solid biomass, such as

wood, animal waste and agricultural residues, to meet their basic energy needs and that solid

biomass accounts for nearly 74 % of total energy use (Brown 2006, Mshandete and Parawira

2009, Amigun et al. 2012, Msibi 2015). This creates substantial potential for biogas

generation to provide health and environmental benefits, especially in rural (farming)


98

communities where poverty levels are high, where a cheaper alternative to electricity is

sought, and where sufficient organic waste is available as feedstock (Amigun and Von

Blottnitz 2010, Smith 2011, Amigun et al. 2012, Biogas 2013, Msibi 2015, GreenCape 2016,

SAGEN and SABIA 2016, GreenCape 2017a, Msibi and Kornelius 2017).

1.1.2.3 The potential of increasing the footprint of biogas generation in rural areas with

government support

There are several developers and governmental programmes working to implement biogas

projects within the rural sector supporting the notion by making energy more accessible and

affordable to disenfranchised communities, the health and well-being of communities will

change for the better. The South African National Energy Development Institute (SANEDI)

is currently responsible for managing and rolling out the Working for Energy Programme, a

renewable energy initiative focused on providing thermal energy and improving the quality of

life for people in rural communities. They are involved in three initiatives totalling about 190

active digesters, which include the Melani Village Biogas Expansion Project, the Illembe

District and Mpufuneko Biogas Projects (SAGEN and SABIA 2016). The project is an

ongoing and funded by the Department of Energy (DoE) through their subsidiary, SANEDI

(UFH 2017). The formation of the Southern Africa Biogas Industry Association (SABIA)

underscores the anticipation of the growth of the biogas industry in South Africa (ESI-

AFRICA 2016).

1.1.3 The environmental potential of biogas production as a sustainable agricultural

practice

In response to growing stress on environmental systems and natural resources, the National

Framework for Sustainable Development (NFSD) commits South Africa to a long-term

programme of resource and impact decoupling and outlines principles and trends regarding

sustainability, as well as a set of implementation actions (DEA 2013). The Department of

Environmental Affairs (DEA 2017) states that is imperative that the energy mix should take

into account its potential environmental impact and should address sustainability by amongst

others mitigating the effects of climate change.

For the purpose of this paper, environmental potential is defined as “the environmental

capacity of structures, processes and functions of ecosystems, bringing together natural


99

physical, chemical, physiographic, geographic and climatic factors, and further integrating

these conditions with anthropogenic impacts and activities of concern, to ensure procurement

of environmental sustainability”.

It is maintained that environmental potential can be realised in the agricultural sector for the

following reasons:

1.1.3.1 The potential to contribute to the reduction in greenhouse gas emissions

The South African government has committed to a 34 % reduction in greenhouse gas

emissions by 2020 (Teljeur et al. 2016), and GreenCape (2017a) believes that farm-scale

biogas generation could save on carbon emissions especially when used as an alternative fuel.

Torquati et al. (2014) regards the contribution it can make to reduce CH4 emissions from the

natural decay of organic matter, and in the overall decrease in CO2 emissions that can be

brought about by the use of alternative energy sources as significant. ESI-AFRICA (2016)

states that local biogas production is further stimulated by the prevailing biogas feed-in tariff

and recent environmental legislation which encourages the establishment of biogas plants, i.e.

the National Environmental Management Act (NEMA), the National Environmental

Management: Waste Act (NEM:WA), the National Environmental Management: Air Quality

Act, the National Waste Management Strategy (NWMS) and the Income Tax Act

Amendment 12L (Cleaner Development Mechanism).

1.1.3.2 The potential to supply renewable energy

South Africa also has a very specific electricity load profile that does not necessarily match

the period of highest solar energy generation, nor does wind energy profiles fit in predictably

with this demand profile (Griffiths 2013). This leaves a gap for biogas electricity generation

to alleviate peak hour demand. As long as the plant is maintained and correctly supplied with

feedstock, generation from biogas is not dependent on any external conditions, making it very

suitable for agricultural use (Griffiths 2013, GreenCape 2017a). Tiepelt (2017) regards the

farming community as the ideal take-off as it can make use of the energy as well as the heat

that is generated.


100

1.1.3.3 The potential to contribute to soil health and increased food production

Ecosystem services that are potentially delivered through the application of organic matter

(OM) are increased carbon (C) sequestration in soils, improved water quality, decrease of

local pollutants and improvement in water quality, reduced erosion, better soil structure and

water holding capacity and ultimately an increase food production (Ji-Quin and Nyns 1996,

De Neve et al. 2003, Mtambanengwe and Mapfumo 2005, Lantz et al. 2007, Mwakaje 2008,

Fonte et al. 2009, Onwosi and Okereke 2009, Yongabi et al. 2009, NERSA 2013). Among

the varied available organic wastes, biogas residue was found to be more efficient for

promoting the soil microbiological activity, and substrate-induced respiration increased with

the high amount of easy-degradable carbon that resulted from higher plant growth (Makádi et

al. 2012). As the use of anaerobic digestion is known to destroy pathogens, using manure as

feedstock on site could potentially reduce the spread of unwanted pathogens and detrimental

nitrate accrual in the water table (Paavola and Rintala 2008, SAGEN and SABIA 2016).

2. Materials and methods

Two self-administered electronic surveys (Babbie and Mouton 2001) were constructed: (S1)

Farmers without biogas digesters, and (S2) Farmers with biogas digesters. The S1 survey

(APPENDIX C) was sent to 25 farmers and responses were received from 10 participants.

The S2 survey (APPENDIX D) was sent to nine farmers, and responses were received from

five. The purposive sample size for S2 (farmers with biogas digesters) is small, as it was

found to be extremely difficult to locate farmers who have installed on-farm digesters for

their own use. The details of all of the participants are summarised in Table 1.

For S1, the study identified farmers not only with high quantities of suitable feedstock types,

but with a variety of feedstock types in different areas of the country. For S2, the study only

focused on farmers who have installed, operated and maintained biogas generators at their

own cost; and not on biogas digesters which have been installed on farms on a commercial

scale or that are installed, operated and maintained at the cost of the developer or in a joint

venture with a developer.


101

Table 1: Details of farms without biogas digesters (S1), and farms with biogas digesters (S2)

as incorporated into this study.

Farmers without biogas digesters (S1)

Name Location Type

Mhlati sugar Pongola, KZN Cultivate sugarcane, export

citrus/mangos/pecan & macadamia

nuts

Waterkloof Williston, NC Sheep farming

Albertina Koppies district, FS Cattle, sheep, crops (maize, sunflower,

soy beans)

De Vlei De Doorns, WC Table grape production

Mariendahl Stellenbosch, WC Cattle, sheep, pig farming

Goedgeleë Overberg district, WC Grain, dairy, wool sheep

Doornfontein Malmesbury, WC Dairy, wine grape, roll on lawn, sheep

Elandsfontein Britstown, NC Organic sheep farming, livestock and

crop production

Kendal poultry farm/Fair

Acres

Lanseria, MP Egg production

Lazena Farm and various

contract farms

Gordon’s Bay, WC Broiler chickens and abattoir

Farmers with biogas digesters (S2)

Name Location Type Year

(installer)

Riverside Piggeries Pretoria, Gauteng Piggery 2015

(ACRONA SA)

No2Piggeries Queenstown, KZN Piggery and dairy 2014

(iBert)

Swineline Cullinan, Gauteng Piggery 2012

(Self-installed)

Uilenkraal Darling, WC Dairy and animal feed

factory

2013

(CAE)

Welgevallen

Experimental Farm

Stellenbosch, WC Semi-commercial

dairy, fruit, vines,

sheep and aquaculture

2015

(Sustainable

engineering

consultants and self-

installed)

The reasoning was to focus on the benefits and challenges facing farmers alone, and not to

cloud the investigations with issues affecting developers. This study also made use of SABIA

(South African Biogas Industry Association), SELECTRA, biogas development/instalment

companies such as BiogasSA, AGAMA BiogasPro and iBert, as well as other experts in the

field to locate the farmers with biogas digesters. Each participant was initially contacted by

telephone and surveys were sent and received via email. This was in many cases followed up

by in-depth telephone conversations.


102

3.0 Results

3.1. Comparative analyses of awareness and understanding of sustainability between

both farmers without biogas digesters (S1) and farmers with biogas digesters (S2)

All of the participants stated that they are aware of the term sustainability, but 20 % of both

S1 and S2 participants could not distinguish between the terms organic and sustainability.

80 % of participants for both surveys could complete the definition of sustainability stating

that “sustainability is the process of utilizing and living within the limits of available

physical, natural and social resources in ways that promote social, ecological and economic

sustainability”, while one participant in S1 stated that the process of sustainability only

promotes ecological sustainability, and another participant in S2 stating that it only promotes

social and economic sustainability. All of the participants in both surveys (S1 and S2) felt

that farmers should incorporate more sustainable practices in South Africa. The 90 % (S1)

and 100 % (S2) were of the opinion that this is what consumer’s demand, while one

participant (S1) thought that there is only a consumers’ demand in certain niches. All of the

S1 participants were of the impression that it is not too late for farmers to incorporate more

sustainable practices into their farming approach.

70 % of S1 participants replied that the electricity crisis in South Africa affects agricultural

practices which results in financial losses. All S2 participants agreed with this statement,

whereas 100 % of both S1 and S2 participants believes that generating environmentally

friendly electricity would promote sustainability for the country.

Farmers with biogas digesters (S2) were slightly more optimistic regarding sustainable

agricultural practices and the role of biogas generation in sustainable development, with 40 %

stating that they are living in a sustainable manner and 60 %, that they are not yet living in a

sustainable manner, but that they are trying to achieve it. On the other hand, only 20 % of

farmers without biogas digesters (S1) lived in a sustainable manner, with 40 % not doing so,

but trying to achieve this (Figure 1).

The majority (80 %) of S2 participants agreed that the implementation of a biogas digester

contributes towards sustainability. One participant disagreed, but it was established that this

particular participant’s understanding of sustainability was misconceived.


103

Figure 1: Efforts by S1 (farmers without biogas digesters) and S2 (farmers with biogas

digesters) towards living in a sustainable manner.

3.2. Comparative analyses of awareness and understanding of climatic changes between

both farmers without biogas digesters (S1) and farmers with biogas digesters (S2)

The level of awareness and understanding of climate change by both S1 and S2 participants

were extremely high. All S2 participants indicate that they have an understanding and

knowledge of climatic changes and GHG emissions. All S1 participants stated that they are

aware of climatic changes; 80 % are aware that methane (CH4) and carbon dioxide (CO2) are

some of the biggest contributors towards climate change and 90 % stated that they are aware

that agricultural activities produce methane and carbon dioxide in large uncontrolled

quantities. 90 % of S1 participants stated that changing climatic conditions have an negative

effect on their agricultural practices, referring to season changes i.e. lower annual rainfall,

water availability, extreme droughts, acid rain and temperature fluctuations, where all of

these negatively affect the economic viability of their farming practices (i.e. higher maize

prices due to lower rainfall, lower milk production due to higher temperatures, poultry

mortalities, lower immunity of livestock against diseases, change in shifting crop cycles and

production, often resulting in smaller crops and lower production).

One of the S1 participants noted that these known effects of climatic change has adjusted the

mind-set of some farmers towards taking social responsibility of GHG emissions and climate

change.

0%

20%

40%

60%

80%

100%

Living in sustainablemanner

Not yet living insustainable manner,

but trying

Not living in asustainable manner

Par

tici

pan

t p

erc

en

tage

(%

)

Sustainability effort of farmers

Survey 1 - Farmerswithout biogasdigester

Survey 2 - Farmerswith biogas digester


104

Figure 2: The level of S1 participants’ awareness of climatic change contributors, and effects

on agricultural practices for farmers without biogas digesters.

3.3 Results for S1 participants – farmers without biogas digesters

3.3.1 Biogas generation awareness, waste management, fertiliser usage and

electricity demand and supply

3.3.1.1 Participant awareness of biogas digester technology

The majority of the S1 participants (80 %) are aware of biogas digester technology; the

20 % who indicated that they are unaware of a biogas digester are livestock farmers located

in the Northern Cape Province and Free State Province of South Africa. All S1 participants

were able to identify that biogas generation is the natural anaerobic decomposition of organic

material to collect carbon dioxide (CO2) and methane (CH4), and to use the methane to

generate energy in the form of gas or electricity.

3.3.1.2 Waste disposal management

S1 participants identified the following waste streams applicable to their farming practices:

animal manure (70 % of the participants), organic plant matter (40 % of the participants),

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Climaticchanges

Agriculturalactivities

produce CH4and CO2 in

highuncontrolled

quanities

Climaticchanges have

negativeeffect on

agriculturalpractices

CH4 and CO2,two of biggestcontributorsto climatic

change

Wastedisposalthrough

biologicalprocesses

Reutiliseorganic

waste, useCH4 to

generateenergy

Par

tici

pan

t p

erc

en

tage

(%

)

S1 participants' awareness of climatic change and waste disposal

Climatechangeawareness

Wastedisposalawareness


105

animal body parts (40 % of the participants), plastics (30 % of the participants) and waste

water (30 % of the participants). Participants could choose more than one waste stream.

Figure 3: Major agricultural waste streams applicable to S1 participants.

Participants indicated that these agricultural waste streams on their sites are currently

managed and disposed through the following methods (Figure 4): burning (30 %), transport

to landfill site (30 %), crop waste recycled for feed (cattle and sheep) (10 %), organic plant

matter reused as soil amendment (20 %), animal manure worked into soil/spread on crops and

plantations as soil amendment to increase soil organic matter (60 %). Household waste

(plastic bags, cans and cardboard) is delivered to municipal solid waste facilities where it is

recycled (40 %). Where free range is practiced – no animal waste (10 %) was reported.

Participants could choose more than one method to manage waste streams.

70 % of participants are aware of biological means to get rid of agricultural waste, with 90 %

confirming that they are aware that animal waste, organic plant matter and abattoir waste can

be used to generate methane for cooking, heating and to generate electricity (Figure 2).

The cost associated with waste disposal varied significantly per participant, on all levels of

agricultural practice. 60 % of participants had zero costs associated with waste disposal, for

30 % costs ranged between R1 000 to R5 000 per month, with one outlier noted of R200 000

per month.

The majority of participants that did incur waste disposal costs noted that waste was routinely

repurposed to save on these costs and showed innovation in using aerobic decomposition to

repurpose their waste:

pig manure is washed off in water-driven channels and flushed into cement tanks,

stirred and pumped over sieves to separate liquid and solids, the liquid ferments in

holding dams and gravitates into a larger rainwater dam from where irrigation takes

0%

20%

40%

60%

80%

100%

Animal manure Organic plantmatter

Animal bodyparts

Plastics Waste water

Par

tici

pan

t p

erc

en

tage

(%

)

Major agricultural waste streams


106

place; dairy waste water is also directed to a holding dam from where it is applied as a

liquid fertiliser during irrigation,

solids are spread on pastures in lieu of fertiliser,

bedding (straw and cattle or sheep manure of cattle and sheep) are left to rot during

winter months and/or

dead animals are buried in trenches.

Figure 4: An illustration of methods used by S1 participants to dispose of their agricultural

waste.

3.3.1.3 Fertiliser usage

While 60 % of participants indicated that they use raw forms of manure or sludge as soil

amendment for soil preparation, 70 % stated that fertiliser remains a major farming expense.

No participants used raw sewage from waste water treatment works as soil conditioner for

soil preparation.

3.3.1.4 Electricity demand

90 % of the S1 participants do not generate their own electricity, with only one participant

admitting to partly making use of solar power generation. Participants indicated the absence

of known governmental incentives or rebates for the generation of environmentally friendly

(green) electricity as a reason for not generating their own electricity.

0%

20%

40%

60%

80%

100%

Animalmanure

worked intosoil or

spread oncrops

Solidmunicipalwaste sentto recycling

facility

Burning Transportedto landfill

site

Organicplant

matterreused as

soilamendment

Crop wasterecycled foranimal feed

Free range,no animal

waste

Par

tici

pan

t p

erc

en

tage

(%

)

Waste disposal method


107

All participants are connected to the Eskom grid for electricity supply, of which 80 % stated

that electricity is a major expense on the farm. 60 % of participants admitted to experiencing

power cuts that influence their agricultural practices, ultimately leading to financial losses;

30 % experience power cuts that influence their agricultural practices, without any financial

losses, and only 10 % of participants indicated that they do not experience power cuts.

Figure 5: Illustrating the degree to which S1 participants are affected by power cuts

S1 participants indicated the following energy sources in use on their farms: electricity, gas

and fuel wood (40 %); electricity and fuel wood only (20 %); electricity only (20 %);

electricity and gas only (20 %). It was also indicated that all farm workers make use of

electricity, 60 % use gas and 60 % use wood.

3.3.1.5 On-farm generation of electricity

40 % of participants stated that the main reasons why they do not invest in generating their

own electricity is that it is too expensive to install a new electricity generating process, 40 %

had insufficient knowledge, 20 % preferred the convenience of Eskom and 10 % found

investing in new processes too time consuming. No participants implied that technology

cannot be implemented on their farm (Figure 6). Participants were able to choose more than

one answer.

60%

30%

10% Percentage of participants thatexperience power cuts affecting theirfarming practices and leading tofinancial losses

Percentage of participants thatexperience power cuts affecting theirfarming practices but not leading tofinancial losses

Percentage of participants that do notexperience power cuts


108

Figure 6: Main reasons why S1 participants do not invest in generating their own on-farm

electricity.

3.3.1.6 Awareness of benefits regarding biogas generation

Figure 7: The percentage of S1 participants that was unaware of 10 given benefits of biogas

generation.

The S1 survey suggested a list of 10 potential benefits derived from biogas generation: 70 %

were unaware of greenhouse gas emissions grants; 40 % were unaware of the potential of

biogas generation to alleviate poverty; 40 % were unaware of potential health benefits, 30 %

were unaware of its potential in the fertiliser industry; 30 % were unaware of its potential to

improve crop quality and soil fertility, 10 % were unaware of the potential of methane gas

production on commercial or domestic scale, 10 % were unaware of the potential growth of

the green economy (job creation/skill development), 10 % were unaware of its potential to

0%

20%

40%

60%

80%

100%

Too expensive Do not knowenough

Easier to stick towhat we know

(Eskom)

Too timeconsuming

Technology notcompatable on

farm

Par

tici

pan

tp

erc

en

tage

(%

)

Reasons for not investing

0%

20%

40%

60%

80%

100%

GHGemmision

grants

Alleviatepoverty

Healthbenefits

Growth ofpotentialfertiliserindustry

Improve cropquality & soil

fertility

CH4 gasproduction(Domestic -commercial)

Growth ofgreen

economy

Heat andelectricitygeneration

Reduction ofwaste

Utilization ofCH4

Par

tici

pan

t p

erc

en

tage

(%

)

Benefits of biogas generation


109

generate heat and electricity, 10 % were unaware of its potential to reduce waste (over-

capacitated landfills) and 10 %, were unaware of the potential to utilise methane gas.

3.4 Results for S2 participants – farmers with biogas digesters

3.4.1 Basic overview of digester characteristic, electricity demand and financial feasibility

of participants

Table 2 gives an overview of the characteristics of digesters installed by the farmers, the

purpose of the digester, as well as the financial feasibility of the operation according to the

participants. The identities of the participants, together with some financial values are

confidential on request.

The participants also stated that the majority of these projects were not subsidised in any way

by the government or government incentive driven program, with the exception of one

digester, which was funded by external investors. All participants who use their biogas to

generate electricity do not get any financial rebates from government for GHG mitigation.

Furthermore, 40 % of participants were introduced to biogas digesters (BD) by a South

African biogas digester company, 40 % were introduced to biogas digesters in another

country, and 20 % heard about it by a friend/colleague/family or none of the above. However,

none of the participants consulted online sources (Figure 8). Participants could choose

multiple answers.

Figure 8: S2 participants’ first source of introduction to biogas digesters.

0%

20%

40%

60%

80%

100%

RSA BD company In another country Other friend/colleague/family Read online

Par

tici

pan

tp

erc

en

tage

(%

)

Source of introduction


110

Table 2: An overview of the cost, scale, type, application, financial indicators and hindrances experienced by S2 participants.

(*Participant identities and some financial values are kept confidential on request from the farmers)

Participants Start-up

cost

Scale/

output

Digester

type

Purpose Waste

usage

Cost

savings on

electricity

per month

Major

hindrance

experienced

Electricity

is a major

expense on

the farm

Financially

viable

according

to

participant

Participant 1 R 500 000 - Plug-

flow

digester

Research 40.248

m3

- Constant

operation (daily

check-ups)

YES Not at the

moment,

potentially

in future

Participant 2 R 5

million

50 kW Covered

lagoon

digester

Electricity

generation

150 t R 22 000 Unpredictability

of microbiology

YES YES

Participant 3 R 6.5

million

190 kW Dome

type

digester

Electricity

generation

500 t

DM

R 72 000 Capital costs

too high

YES NO

Participant 4 R 10

million

400 kW Plug-

flow

digester

Electricity

generation

3 046 t R 80 000 Costs to run

plant

NO,

however it

is

significant

Not at the

moment,

potentially

in future

Participant 5 - 75 kW Agitated,

not

heated,

HRT 50

Electricity

generation

and hot

water

generation

400 t Could not

determine

Capital

investment

YES YES



111

3.4.1.1 Feedstock usage, water usage and waste disposal

All S2 participants make use of a single feedstock (either pig or dairy effluent); none make

use of co-digestions of varied types of feedstock. The results showed that water usage per

digester was minimal, if not zero, due to the high liquid content of the the wet matter (eg.

dairy and piggery effluent). 90 % of participants stated that before implementing a biogas

digester, organic waste was disposed through evaporation dams/ anaerobic ponds for fertiliser

irrigation/composting/fertiliser. One participant stated that not all manure is diverted to the

biogas digester and that manure is still used partially as fertiliser.

3.4.1.2 Fertiliser usage and digestate utilisation

40 % of S2 participants felt that fertiliser is major expense on the farm. 60 % of participants

use additional manure/WWTW sludge as soil conditioner for soil preparation; 60 % use their

digestate as by-product from their biogas digester operation as soil conditioner/soil

amendment and 40 % do not use their own digestate as soil conditioner/soil amendment, but

aim to do so in the future. Only 20 % of participants sell their digestate for fertiliser

production.

3.4.1.3 Storage and utilisation of biogas digester by-products (biogas/digestate)

None of the participants stored any products from the biogas digester (biogas/digestate). 60 %

of participants use all biogas produced, with only one participant using excess biogas to

generate heat.

3.4.1.4 Electricity access

60 % of participants are connected to the national Eskom electricity grid; 40 % stated that

their farm workers get access to the products (only electricity).

3.4.2 Participants’ opinion of biogas generation potential in South Africa

80 % of participants indicated that, according to their experience, there is potential for

medium scale biogas digesters with an output scale of >30 kW and <1 MW (Refer to

APPENDIX B for scale guideline). One participant mentioned that there is only potential for

small-medium scale operations if feedstock is free and when excess heat is used. Other


112

participants commented that financial viability of small-scale projects have increased and will

continue to increase due to the sharp increases in electricity recently and other participants

were positive about the potential of small-scale use of own gas. In contrast, one participant

was adamant that biogas projects on this scale are not viable and based his statement on

personal experience with an installation that was not cost-effective.

All participants agreed that large-scale projects with an output of >1 MW have potential,

providing that the technology is effective. One participant mentioned that the

adaptability/ease of operation of small-medium and larger scale biogas facilities makes it

possible to relieve peak electricity demands placed on Eskom, and in this way promotes the

potential of the industry.

Participants were asked to suggest biogas digester types which, according to them, showed

the highest potential on farm level. Participants seemed to revert to experience and

recommended what they already have, with suggestions on to existing systems, or exploring

the possibilities of co-digestion. Single feedstock AD was reported to be inefficient, but

preferred as it is biologically more stable. Participants with projects not meeting their

demands and becoming a financial liability were unable to recommend a model with more

potential. All participants stressed that the lack of technical transfer and training and skills

development in the biogas digester industry hinders its potential growth and development.

3.4.3 Operation and employment

Four out of five participants operate the digester on their own, while one participant employs

a dedicated operator. This particular participant showed great frustration with the biogas

digester that was not feasible. The survey indicated that on average, two people were required

to operate this facility. 60 % of the participants agreed that installation of a biogas digester

promoted social sustainability by creating jobs; 40 % disagreed.

One participant in particular stressed that the lack skills for biodigester management could

lead to additional financial losses, negatively affecting a farmer’s motivation to pursue

sustainable agricultural practices.

3.4.4 Benefits experienced

Benefits identified by S2 participants regarding their biogas projects are: treatment of waste

to produce very effective fertiliser; heat (hot water) and electricity generation; reduction in


113

CH4 (mitigate GHG gas emissions, mitigating climatic change); potential to save when

carbon tax is implemented; reduction of pollution especially in terms of waste run-off into

nearby ecosystems (such as river systems); presenting opportunities to learn more about AD

and biogas digesters. However, none of these benefits are applicable to their operation, as the

original aim was to save electricity cost and it is not found to be cost effective at this stage.

3.4.5 Impact of policy and legislation implemented by South African government

In terms of policy and legislation regarding generation of biogas and its by-products locally,

60 % of the participants experience challenges in this regard, as no support is received from

the government. The process of environmental impact assessments required for the

construction of a biogas digester is very expensive and time consuming, carbon tax incentives

are difficult to access for small farm-scale biogas operations and there is an overall lack of

understanding and available expertise regarding biogas generation as an option.

One participant confirmed that agricultural policies and legislations in general hinder

progressive agriculture practices to grow. The lack of knowledge about relevant legislation

was highlighted as a hindrance and could be attributed to the lack of education and

opportunities within the agricultural sector, as well as a lack of support by National Regulator

of South Africa (NERSA).

3.4.6 Reasons given why farmers do not invest in biogas generation

The primary reasons why other farmers do not invest in biogas generation on small-medium

farm-scale was the expense to install a new electricity generating process (100 %); in

addition, further stumbling blocks were the lack of education about the field (60 %);

familiarity with Eskom-supplied electricity (40 %), the perception that this technology will

not work on a specific farm (20 %) and the process is regarded to be too time consuming

(20 %) (Figure 9).


114

Figure 9: Reasons identified by S2 participants on why they think other farmers do not invest

in biogas generation.

4. Discussion

One of the major challenges experienced during this study was to identify and interact with

farmers who installed biogas digesters. There are numerous examples of different

applications of biogas digesters in South Africa, but only a few instances where it was used

solely by farmers. In addition, participants without biogas digesters (S1) were reluctant to

participate in this study as they were unfamiliar with the technology, found it not to be

applicable to their farming practice and that they thus cannot contribute to the study.

The small group of farmers with biogas digesters (S2) voiced their frustration with their

installations. While supporting and understanding the importance of sustainable agriculture

practices, the lack of support, experience, skills and confusing legislation were major

hindrances in their operations and most of these installations have not reached sustainable

feasibility yet, especially with regard to an electricity saving initiative.

The results obtained have been used to evaluate the potential of the agricultural sector to

implement the biogas technologies that would enable economic, environmental and social

sustainability in this sector. The responses received were interpreted in relation to the three

pillars of sustainability as outlined in sections 1.1.1, 1.1.2 and 1.1.3.

4.1 Potential of the agricultural sector to use biogas technology as a means to achieve

economic sustainability:

4.1.1 Potential to supply in energy/heat demands by making use of the availability of

feedstock

0%

20%

40%

60%

80%

100%

Too expensive People areuneducated

Easier, stick toEskom

Time consuming Tech will notwork on farm

Par

tici

pan

t p

erc

en

tage

(%

)

Primary reasons for not investing


115

The majority of the S1 participants were aware of biogas digester technology and of the

potential to generate energy by using agricultural waste as feedstock. All S1 participants

regard electricity as a major expense and a motivation to pursue biogas generation and

indicated that they are largely affected by power outages. The perceived time, money and

effort of implementing new technology however inhibit these farmers from pursuing biogas

technologies, limiting its economic potential. However, everyone agreed that this technology

is compatible with their farming practices.

S2 participants identified its potential for waste management and the generation of renewable

energy as a definite incentive to pursue this technology. The costs incurred with waste

management varied significantly from site to site, and is not seen as a motivation to pursue

biogas generation. The significant amount of agricultural wastes that is available to be used

as feedstock underscores its economic potential. S2 participants support the potential of the

industry if feedstock is free and where excess heat can be used in addition to biogas.

According to their responses that not all the biogas produced is used, and 20 % participants

use the biogas to generate heat, its full potential in terms of energy generation has yet to be

realised.

4.1.2 Potential to produce organic fertiliser that can be used as soil conditioners or

compost

Innovative applications of agricultural waste streams as identified by S1 participants indicate

that, although they are not yet applying biogas technology, the majority see the potential of

agricultural waste streams as a sustainable agricultural practice in terms of fertilising crops,

especially as the majority identified fertiliser costs as a major expense. S2 farmers are using

digestate, or indicated that they will in future. This supports the potential of biogas generation

on farm scale as a mechanism to reuse waste for soil conditioning and to save on fertiliser

costs.

4.1.3 Potential to find affordable financial solutions to the challenges of operational costs

and revenue possibilities

The results obtained with S2 illustrate that even though these farmers have invested in biogas

technology and are saving on electricity cost, capital cost and financial feasibility remains

major hindrances in the further development of this industry and limits its economic


116

potential. Where biogas installation occurs as a joint venture between the farmer and the

developer (e.g. Zandam farm and iBert) (GIZ and iBert 2017, GreenCape 2017c), the

financial risk is reduced and overall financial viability of the project is enhanced (GIZ and

iBert 2017, GreenCape 2017c). This approach may promote the economic potential of the

farm-scale industry (Bio2Watt 2017, iBert 2017, Scharfy et al. 2017).

4.1.4 Potential of accessing realistically available governmental support

The absence of knowledge about a platform of compensation such as governmental

incentives or rebates for the generation of environmentally friendly (renewable) electricity

known to S1 participants undermines the development of the economic potential of biogas

generation. Even though S2 participants invested in this technology, 60 % still identified the

lack of government support and the numerous policy and legislation stumbling blocks as

factors limiting the potential of biogas generation.

4.2 Potential of the agricultural sector to use biogas technology as a means to

achieve social sustainability

4.2.1 Potential to create jobs and opportunities for skills transfer and education

Of the S1 participants a substantial percentage was unaware of the social benefits through the

application of biogas technology. Job opportunities reported by S2 participants does not

necessarily reflect the job creation potential of the industry as the generation facilities

involved are small or farm-scale.

Lack of skills, education and knowledge is however a recurring theme throughout as a

limiting factor for the social, economic and environmental potential of biogas generation.

This is supported by SAGEN and SABIA (2016) that predicts that this skills gap will expand

with the growing market should there be no intervention and standardisation of technical

skills.

4.2.2 Potential to deliver health benefits and improve the standard of living

Electricity is the major source of energy for farm workers, together with gas and fire wood.

S2 participants indicated that farm workers have access to electricity generated through

biogas. Using solid biomass as energy source is however not sustainable (Amigun et al.


117

2012) and creates substantial potential for biogas generation, especially in rural (farming)

communities (Smith 2011, Amigun et al. 2012, GreenCape 2016, SAGEN and SABIA 2016,

GreenCape 2017a).

Tables 3 to 6 quantify the potential of specific feedstocks for energy supply via biogas

generation that will result in health benefits and an improved standard of living when

implemented.

Table 3: Requirements of digester volume and amount of cattle to produce a certain amount

of biogas to supply an associated number of people with energy (Source: Dioha et al. 2012).

Required biogas (m3)

for lighting and

cooking

Required number

of cattle

Required digester

volume (m3)

Number of people

supplied with energy

1 2 – 4 4 Up to 4 people

1.5 4 – 5 6 5 – 6 people

2 5 – 7 8 7 – 8 people

2.5 7 – 9 10 10 – 13 people

3.75 9 – 12 15 14 – 18 people

5 13 – 15 20 19 – 25 people

Table 4: Biogas yield from selected feedstock types.

Feedstock Daily

manure

production

(kg/animal)

% Dry

matter

(DM)

Biogas yield

(m3/kg DM)

Estimated

biogas yield

(m3/animal/day)

Source

Cow manure 8 16 0.2 – 0.3 0.32 Bond and

Templeton

(2011)

Chicken

manure

0.08 25 0.35 – 0.8 0.01

Sewage 0.5 20 0.35 – 0.5 0.04

Pig manure 2 17 0.25 – 0.5 0.128 Surendra et al.

(2014)

Food waste

(Vegetable)

- 5 - 20 0.4 -

Deublein and

Steinhauser

(2008) Organic

household

waste

- 40 - 75 0.3 – 1.0 -


118

Table 5: Number of cattle required to produce 1m3 to generate enough electrical and heat

energy.

Feedstock Required

number of cattle

Amount of

manure

required for

1m3 biogas

per day

Biogas

yield

Electrical

energy

Heat

energy

Number of

people

supplied

with energy

Cow manure A = 3;

B = 2 – 4

25 kg 1 m3 2.1

kWh

2.6

kWh

Up to 4

Source: A = Bond and

Templeton (2011)

B = Dioha et al.

(2012)

Bond and Templeton

(2011)

Arbon (2005)

Dioha et al.

(2012)

The biogas energy generation analyses (Table 6) is used as additional support for the

potential of biogas implementation on farm level to generate and supply energy to farm

workers. With as few as 5 to 7 cows, it is possible to supply energy per day for up to eight

farm workers (Table 3 and Table 6). When only referring to electricity, it is estimated that 50

kg of cow manure is required from 5 to 7 cattle per day to generate 2 m3 of biogas with an

electrical output of 4.200 kWh. This is similar to the average electricity consumption per

capita (4.228 kWh) in South Africa (World Bank 2014).

Table 6: Potential amount of electrical energy generated from biogas produced by the

required amount of cattle and manure, compared to the average demand of electricity per

capita in South Africa.

Feedstock Amount of

manure

required for

2m3 biogas

per day

Required number

of

cattle

Biogas

yield per

day

Electrical

energy

Average

electricity

consumption

per capita in

South Africa

Cow manure 50 kg A = 6;

B = 5 – 7

2 m3 4.200 kWh 4.228 kWh

Source Bond and

Templeton

(2011)

A = Bond and

Templeton (2011)

B = Dioha et

al.(2012)

Bond and

Templeton

(2011)

Arbon

(2005)

World Bank

(2014)


119

Table 7 compares the calorific values of biogas, natural gas, hard coal and firewood and

illustrates how biogas generation can replace these sources of energy. Calorific value of fuel

is the amount of energy released per unit mass/per unit volume when the fuel is burnt

completely (Msibi 2015, em-ea.org 2017).

Table 7: Comparison of calorific value of different energy resources.

Energy

resource

Amount

required

Calorific

value

Source

Biogas

1 m3

26 MJ Arbon (2005)

21 MJ Surendra et al.(2014)

20 MJ Pathak et al. (2009)

Natural gas 0.77 m3 33,5 MJ

Arbon (2005)

Hard Coal 1.1 kg 23.4 MJ

Fire wood 2 kg 13.3 MJ

This illustrates the significant potential of biogas generation to alleviate energy poverty and

improve the general well-being of impoverished communities.

4.3 Implementation potential of the agricultural sector to achieve environmental

sustainability

Both farmers with or without biogas generation facilities on their farms had a sound

understanding of the concept of sustainability and all participants, in both surveys, were

positive towards the implementation of sustainability in agriculture. S2 participants were

slightly more optimistic regarding sustainable agricultural practices and the role biogas

generation plays in sustainable development, while the majority of S1 participants

acknowledged that they are not yet living in a sustainable manner. Current efforts by farmers

in both groups should be incorporated in future practices, underscores the environmental

potential that resides in the agricultural biogas sector.

4.3.1 Potential to contribute to the reduction in greenhouse gas emissions

The level of awareness and understanding of climate change and the negative effects on

agriculture were extremely high for both S1 and S2 participants. In addition, S1 participants

acknowledged the role that agriculture can play in the production of methane and carbon

dioxide. There is no significant lack of knowledge and understanding regarding the


120

generation of methane, the cause and effect of greenhouse gas (GHG) emissions, and the

possibility of energy generation through methane utilisation.

Even so, there is no platform for government compensation for reducing GHG emissions,

forfeiting the incentive to contribute, as it constitutes too big a financial investment/risk. The

majority of (S1) participants indicated that they were not aware of existing financial

incentives for curbing GHG emissions. This creates opportunities for future development

should these limitations be addressed.

4.3.2 Potential to supply renewable energy

Participants in both surveys indicated that biogas generation would promote sustainability

through the provision of a renewable source of energy. S2 participants indicated that they use

most of their biogas for the generation of electricity. This supports the potential of this

technology to deliver renewable energy, in the case of farm-scale operation this would mostly

be appropriated for own use.

4.3.3 Potential to contribute to soil health and increased food production

There is a firm understanding and knowledge of decomposition of organic matter and

reutilisation of organic matter as soil amendment. Farmers that installed biogas digesters use

digestate successfully as soil conditioner and fertiliser. S1 participants also show

understanding of this principle as they apply various innovative methods to use animal and

feedstock wastes to enhance soil properties. This underscores the potential of using the by-

products of digestate and fertiliser on farm-scale.


121

Conclusion

According to literature, biogas generation as a sustainable agriculture practice shows very

high potential for both energy generation and waste disposal in South Africa (Smith 2011,

Abbasi 2012, Amigun et al. 2012, Griffiths 2013, GreenCape 2016, SAAEA 2016, SAGEN

and SABIA 2016, GreenCape 2017a, Tiepelt 2017). This paper supports this statement.

The willingness/non-willingness of participants to partake in this study, gives insight into the

potential of biogas generation in the agricultural sector, as it highlights the limitations on the

industry through existing perceptions and frustrations.

Developing the economic potential of biogas generation will require wide-scale knowledge

transfer about the opportunities it presents. The availability of financial support, whether in

the form of joint ventures, or as incentives or rebates, would enable the industry to grow on

farm level. Current waste management practices including the application of waste streams

for fertiliser use, supports the potential of biogas generation as a means to generate fertiliser

for own use and saving on fertiliser costs.

There is significant promise in using biogas technology to achieve social sustainability,

specifically at farm-scale. Job creation, the opportunity for skills transfer and education, as

well as the potential to deliver health benefits and improve the standard of living in rural or

farming communities, is regarded as substantial.

It is also believed that, through the use of AD, environmental sustainability may be achieved.

Participants were familiar with the concept of sustainability and indicated that they would

like to follow such practices. The potential of pursuing these activities is however limited by

the lack of information about possible rebates in terms of generating renewable energy,

rendering installation of biodigesters an unacceptable financial investment/risk.

The limited availability of information, knowledge and skills, however, reduces the potential

of this industry. Addressing technology transfer specifically would create significant

opportunities to develop this industry in the agricultural sector. This supports various sources

reporting the scarcity of experience required to operate biogas plants in order to optimise the

country’s biogas potential (SAGEN and SABIA 2016, GreenCape 2017a, Mutungwazi et al.

2017, Tiepelt 2017).


122

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131

PAPER 3: DEVELOPING A DECISION-MAKING

TOOL TO EVALUATE THE SUSTAINABLE

POTENTIAL OF ON-FARM BIOGAS DIGESTERS IN

SOUTH AFRICA

Abstract

Biogas generation and use could potentially impact sustainability, especially through the

integration of waste management and energy technologies (Biogas 2013, Bachmann 2015,

SAGEN and SABIA 2016). This makes biogas generation especially suitable in the pursuit of

sustainable agricultural practices (Biogas 2013, Griffiths 2013, SAGEN and SABIA 2016,

GreenCape 2017a, GreenCape 2017b, GreenCape 2017c, Tiepelt 2017). The many variables

in the South African scenario complicate implementation, as it was found that

implementation should be site-specific to be feasible (Lutge 2010, Biogas 2013, Shah et al.

2014, ESI-Africa 2016, Zhu 2016, GreenCape 2017a, GreenCape 2017c, Mutungwazi et al.

2017, Steyn 2017, Tiepelt 2017). A generic model was thus developed as a decision-making

tool to enable the evaluation of the sustainable potential of a specific digester type at a

specific site, taking all the variables into account. The model is based on the scoring of the

three determinants of sustainability namely environmental, social and economic according to

a set of four defining factors. Based on literature and local expertise that was accessed

through interviews, a comparison of the characteristics of the CSTR digester type with

agricultural requirements enabled the identification of the CSTR digester as the type that

could show the most sustainable potential when implemented as a sustainable solution to

address energy poverty, the rising costs of electricity and waste management demands. The

validation of the sustainable potential of the CSTR digester type by applying the generic

model is recommended through further studies to enable the successful implementation of

this digester type according to site-specific needs.

1. Introduction

There is substantial opportunity for the generation of biogas in South Africa, especially in the

agricultural and household waste sector. Renewable energy could provide the much-desired

sustainable rural revitalisation in developing countries and also serve as an ideal cost-


132

effective alternative for waste management and energy generation in low-income and/ or

rural communities in South Africa, especially as energy has been identified as a major

element in the competitiveness and sustainability of the farming sector (Mshandete and

Parawira 2009, Smith 2011, Abbasi 2012, Amigun et al. 2012, Biogas 2013, Griffiths 2013,

NERSA 2013, Carter and Gulati 2014, SAAEA 2016, SAGEN and SABIA 2016, GreenCape

2016, GreenCape 2017b, GreenCape 2017c, Tiepelt 2017).

South Africa has adapted a systems approach to sustainability and is committed to a long-

term programme of resource decoupling that would enable the economy to grow without

compromising environmental integrity (DEA 2008, DEA 2013). Probably the most important

environmental benefits of agricultural biogas use lie in the contribution to reduced CH4

emissions from the natural decay of organic matter (OM) and in the decrease in CO2

emissions by using an alternative to conventional fossil fuels (Torquati et al. 2014).

The collective self-production of gas in rural and urban households with community-based

biogas digesters also show some potential, especially in terms of the relief it can bring to the

demands placed on the national electricity grid (NERSA 2013, GreenCape 2017a).

GreenCape (2016) estimated that the total electricity potentially generated from biogas in

South Africa from agricultural waste is 2 300 MWe (MegaWatt electric). Additionally

Abbasi (2012) predicted that by 2020, the largest volume of produced biogas will emanate

from farms and large co-digestion biogas plants that are incorporated into farming and food-

processing structures.

The task on hand is to identify the production system that has the most sustainable potential

and therefore could benefit farmers’ quest for a more sustainable future. However, the many

variables in the South African biogas generation scenario complicate sustainable

implementation, as the design of a digester is influenced by various logistic and social factors

such as health and job creation, and therefore it is recommended that farm-scale

implementation in South Africa should be tailored to be site-specific (Lutge 2010, Biogas

2013, Shah et al. 2014, ESI-Africa 2016, Zhu 2016, GreenCape 2017a, GreenCape 2017c,

Mutungwazi et al. 2017, Steyn 2017, Tiepelt 2017).

Lutge (2010) further stated that average values tend to mask any potential benefits,

particularly when using a function to estimate the cost of a biogas plant, as there are many

variables that determine the choice of plant. Mutungwazi et al. (2017) concluded that even

though their study identified the in situ-cast concrete digester (Puxin) as the most suitable


133

digester for energy generation on small/household scale in South Africa, stakeholders should

still do their own selection based on the analyses of their own situation and design.

The following digester types were identified as having sustainable potential with regards to

biogas generation in the agricultural sector in South Africa: CSTR (continuously stirred tank

reactor), lagoon digester, up-flow sludge blanket (UASB), plug-flow digester and fixed-film

digester. Mutungwazi et al. (2017) found the in-situ cast concrete digester (Puxin) to be the

most suitable (not necessarily having the highest sustainable potential) small-scale design for

installation in the South African context (APPENDIX E).

The choice of the design of the digester is thus a key determinant in the feasibility of its

implementation. This paper proposes a generic model to determine the digester type with the

highest sustainable potential for different hypothetical sites.

The paper further motivates the CSTR digester type for implementation on farm-scale. The

digester type was identified by comparing its characteristics to the requirements of the

agricultural sector. This choice of digester type will however have to be validated by

applying the proposed generic model on site.

2. Materials and methods

A generic model was conceptualised that could be applied to determine sustainable potential

of specific biogas digesters on farms. Face-to-face semi-constructed interviews (Babbie and

Mouton 2001) were conducted with key roleplayers in this discipline. These included among

others, representatives of the South African Biogas Industry Association (Tiepelt 2017) and

GreenCape (2017a), a non-profit organisation that drives the widespread adoption of

economically viable green economy solutions from the Western Cape. In addition to

available literature including webpages, brochures, policy documents and developer’s

implementation specifications, biogas plant developers and installers such as Botala Energy

Solutions (Steyn 2017) were consulted telephonically and via email.

Secondly, the characteristics of digester types were considered and compared to the

requirements of the agricultural sector to identify the digester type with the highest

sustainable potential when applying the generic model on site.

The methodology process followed to develop the model and demonstrate possible

implementation is illustrated in Figure 1.


134

Figure1: Flow chart illustration of the methodology approach

MAJOR OBJECTIVE Develop a generic model to determine the farm scale digester type that would show the most sustainable potential in a specific set of circumstances

GENERIC MODEL Hypothetical scoring of digester types according to sustainability categories:

- Economic factors - Social factors - Environmental factors

INTERPRETATION OF SUSTAINABLE POTENTIAL SCORE (SPS)

IMPLEMENTATION OF GENERIC MODEL

COMPARISON OF FARM SCALE DIGESTER TYPES - Continuously stirred tank reactor (CSTR) digester - Lagoon digester - Up-flow sludge blanket (UASB) digester - Plug-flow digester - In-situ Cast (Puxin) digester

• - Fixed-film digester • - In-situ cast

CHOICE OF DIGESTER Demonstrates highest sustainable potential compared to others, for agricultural practice in South Africa:

- CSTR Digester type

RECOMMENDATION Further studies to validate the sustainable potential of the CSTR model for on-farm use by applying the generic model as a decision-making tool.

SUSTAINABLE POTENTIAL SCORE (SPS)


135

2.1. Constructing a generic model to determine the sustainable potential of a biogas

digester for farms

In this study, the development of a generic model to score the sustainable potential of a

biogas digester in a site-specific context is based on the hypothetical calculation of

sustainable potential. This model focuses on the dynamics of on-farm biogas digester

implementation according to the South African situation. While a study by Juarez-Hernandez

and Castro-Gonzalez (2016) also made use of a scoring method, it only considered the impact

of biogas on the energy sustainability of an urban restaurant in Mexico; Scharfy et al. (2017)

also calculated scores for three sustainability categories (economic, social and ecology), but

for the purpose of evaluating clean technologies in general for agricultural practices in

Switzerland.

The first step of this study was defining the three sustainability categories (SC) (i.e.

economic, social and environmental) and the factors (SCFs) that impact on each category.

(Table 1); secondly, a score out of 5 was allocated for each of these factors (SCFs) within

each category (SC) (Table 5). Each digester type was rated out of 20 for its combined

economic potential (CEPa), combined social potential (CSP) and combined environmental

potential (CEPb) based on the factors determined by literature, which are detailed in Table 1

(Dennis and Burke 2001, Arbon 2005, Jenkins et al 2007, Tambone et al. 2007, Schleiss and

Barth 2008, Tambone et al. 2009, Amigun and Von Blottnitz 2010, Lutge 2010, Amigun et

al. 2011, Dillon 2011, GreenPeace 2011, Smith 2011, Abbasi 2012, Makádi et al. 2012,

Biogas 2013, DEA 2013, NERSA 2013, EPI 2014, GreenCape 2014, Ruffini 2014, Shah et

al. 2014, Torquati et al. 2014, Msibi 2015, DEA 2016, DoE 2016, ESI Africa 2016,

GreenCape 2016, SAAEA 2016, SAGEN and SABIA 2016, Atkins 2017, BiogasSA 2017,

Culhane 2017, DEA 2017, GreenCape 2017a, GreenCape 2017b, Kumba et al. 2017, Msibi

and Kornelius 2017, Steyn 2017, Tiepelt 2017, Tradingeconomics.com 2017).

The total sustainability potential value (TSPV) out of 60 was calculated for each digester.

The total sustainability potential percentage (TSPP) is used to determine the sustainability

potential score (SPS). The sustainability potential score (SPS) places the biogas digester type

in a specific sustainable potential category (SPC) (Table 2), illustrating the digester’s

sustainable potential.


136

The equation below illustrates the proposed SPS calculation for a digester type:

𝐷𝑖𝑔𝑒𝑠𝑡𝑒𝑟 𝑡𝑦𝑝𝑒 𝑆𝑃𝑆 = [(𝐶𝐸𝑃𝑎 + 𝐶𝑆𝑃 + 𝐶𝐸𝑃𝑏)

60] × 100 ÷ 20

Biogas generation impacts all three principles of sustainability namely environmental, social

and economic (Dennis and Burke 2001, Arbon 2005, Greben and Oelofse 2009, Kuhlman and

Farrington 2010, Morelli 2011, Potgieter 2011, Smith 2011, Biogas 2013, DEA 2013, EPI

2014, DEA 2016, DoE 2016, SAGEN and SABIA 2016, Teljeur et al. 2016, DEA 2017,

GreenCape 2017a, GreenCape 2017b, Mutungwazi et al. 2017, Tiepelt 2017). Therefore, it is

essential to define sustainability, sustainable potential and the categories of sustainable

potential used to calculate the sustainable potential of a biogas digester per specific

site/environment.

In this paper, sustainability is defined as: “The process of utilising and living within the limits

of available physical, natural and social resources in ways that promote social, ecological

and economic sustainability all at the same time, while allowing the living systems in which

humans are entrenched to flourish in perpetuity” (UN 1987, DEA 2008, Kuhlman and

Farrington 2010, Morelli 2011, EPI 2014, Uwosh.edu 2017).

2.1.1 Sustainable potential

In this paper, sustainable potential is defined as: “The possible capacity of using physical,

natural and social resources within their available limits and in ways that promote the

development and growth of social, ecological and economic sustainability all at the same

time, while allowing the living systems in which humans are entrenched to flourish in

perpetuity” (Howarth 2012).

2.1.1.1 Economic potential

The economic potential is defined as: “The subset of the available technical potential that is

available in terms of biogas generation, where the cost required to generate the energy

(which determines the minimum cost required to develop the resource) is less than the

revenue available in terms of displaced energy and displaced capacity” (Brown et al. 2016).


137

2.1.1.2 Social potential

The social potential refers to: “Social issues and related indicators that can enhance social

conditions such as job-creation, health and well-being in South Africa related to the

sustainable development of biogas generating facilities” (Amigun et al. 2011, Msibi and

Kornelius 2017).

2.1.1.3 Environmental potential

The environmental potential is defined as: “The environmental capacity of structures,

processes and functions of ecosystems, bringing together natural physical, chemical,

physiographic, geographic and climatic factors, and further integrating these conditions with

anthropogenic impacts and activities of concern, to ensure procurement of environmental

sustainability” (Akella et al. 2009).

2.1.2 Scoring of sustainable potential methodology

2.1.2.1 Calculating sustainable potential score (SPS)

The hypothetical calculation of potential was done by scoring the three sustainable categories

(SCs) based on the four sustainable category factors (SCFs) applicable to each category. The

total sustainability potential value (TSPV) is calculated which is a total combined value out

of 60 for the combined economic potential (CEPa), combined social potential (CSP) and

combined environmental potential (CEPb) of each digester. From the total sustainability

potential percentage (TSPP) the sustainability potential score (SPS) is calculated (Table 5) to

determine the sustainable potential category (SPC) within which the digester would fall

(Table 2).

2.1.2.2 Sustainable Categories (SC) and Sustainable Category Factors (SCF)

Four sustainability category factors are defined for each of the sustainable categories i.e.

economic, social and environmental (Table 1).


138

Table 1: The definitions of the four sustainable category factors (SCF) for each sustainable category (SC) i.e. economic, social and environmental.

SUSTAINABILITY CATEGORY FACTORS DEFINITIONS

SUSTAINABLE

CATEGORY (SC)

SUSTAINABLE

CATEGORY

FACTORS (SCF)

DEFINITION

ECONOMIC Technical Gas production and energy efficiency, temperature sensitivity and water requirements, structure robustness

and lifespan, availability of feedstocks

Fertiliser production Sufficient amount and composition of fertiliser for own use or resale of soil condition/compost

Financial Initial capital cost (including installation) required, operational cost. For example: expected revenues (based

on local market prices) minus generation costs, considered over the expected lifetime of the generation asset;

or generation costs relative to a benchmark (e.g. a natural gas combined cycle plant) using assumptions of

fuel prices, capital cost, and plant efficiency

Governmental

support

Policy and legislation support in terms of subsidies, incentives or programmes, as well as realistic support

duration to initiate gas and energy production from installation

SOCIAL Job creation Amount of jobs created with sufficient job satisfaction, new skills development and training

Health benefits and

energy use

Improvement in living standards, general well-being and access and use of energy sources

Convenience and

access

User friendly and accessible, difficult to use and not so accessible, in-depth training or expertise needed

Governmental

support

Policy and legislation for quality assurance and ability to implement; education facilitation

ENVIRONMENTAL GHG mitigating

effects

Sufficient use of biogas generated to decrease greenhouse gasses

Waste management Tonnage of waste redirected from landfills

or reused

Fertiliser utilization Quality composition of fertiliser applicable to environmental standards of fertiliser use

Governmental

support

Renewable resource use and carbon mitigation



139

2.1.2.3 Sustainable Potential Categories (SPC)

The sustainable potential scores (SPSs) illustrated in Table 5 were used to determine the

sustainable potential category (SPC) (Table 2) for each digester type. The sustainable

potential categories (SPCs) are defined as follows:

*Note: It is important to note the difference between SC and SCF, refer to section 2.1.2.2.

These definitions are also used for interpretation in section 3.1.2.

Poor potential

Digester type shows poor potential due to a very low sustainable potential score with very

poor economic, social, and environmental sustainable potential, and should not be

considered.

Low potential

Digester type shows low potential due to a sustainable potential score showing

low/fluctuating economic, social, and environmental sustainable potential. Faces many

challenges, with room for improvement in certain/all sustainable categories (SC).

Average potential

Digester type shows average potential due to an average sustainable potential score with

moderate/fluctuating economic, social, and environmental sustainable potential. Faces some

challenges, with room for improvement in a specific sustainable category (SC)/certain

sustainable category factors (SCF).

Good potential

Digester type shows good potential due to high sustainable potential score with sufficient

economic, social, and environmental sustainable potential. Faces few challenges, with small

adjustments needed for improvement in certain sustainable category factors (SCF). Could

therefore be considered for implementation.

Excellent potential

Digester type shows excellent potential due to a very high sustainable potential score with

combined economic, social, and environmental sustainable potential. Faces no/very little and

should be implemented.


140

2.1.2.4 Sustainable Potential Score Categories (SPSC)

Five sustainable potential score categories (SPSC) are proposed assigning a value range to

the sustainable potential category (SPC) against which the SPS per digester type is measured

indicating its sustainable potential. To measure the sustainable potential of each SC

(economic, social and environmental), the CEPa/CSP/CEPb values can be analysed to

determine the SPS for each SC respectively to determine which SC is underscoring and

requires improvement to in essence improve the score of each SC and therefore improve the

over-all SPS of a digester type. These same measurement categories (SPSC) (Table 2) of

potential can also be used to rate the value (out of 5) given to each SCF.

Table 2: Illustrates the five sustainable potential score categories SPSC against which the

SPSs are measured for each digester type.

Sustainability potential score categories (SPSC)

Economic

potential category

factor

Social potential

category

factor

Environmental

potential

category factor

Sustainability

potential

category (SPC)

1–1.9 Poor 1–1.9 Poor 1–1.9 Poor 1–1.9 Poor

2–2.9 Low 2–2.9 Low 2–2.9 Low 2–2.9 Low

3–3.9 Average 3–3.9 Average 3–3.9 Average 3–3.9 Average

4–4.9 Good 4–4.9 Good 4–4.9 Good 4–4.9 Good

5 Excellent 5 Excellent 5 Excellent 5 Excellent

2.2 Identifying the most sustainable digester type to enable the implementation of the

generic model

A comparison of characteristics of biogas generation (Table 3) enabled the evaluation of

these characteristics against the requirements of the agricultural sector. This facilitated the

identification of the most suitable digester type for agricultural application on a selected site,

by applying the generic model (Table 5).

2.2.1 Comparison of characteristics

There are numerous digester types applicable to farm scale AD (APPENDIX E) that varies in

efficacy and feasibility (Hamilton 2014). Levels of efficiency also vary between reactor types

and specific situations (Lutge 2010, Hamilton 2014, GreenCape 2017a). Tables 3 and 4


141

compare the characteristics considering feedstock, Hydraulic Retention Time (HRT), biogas

yield, difficulty of technology and operational mode.


142

Table 3: A comparison of the characteristics of digester types considered in this study (Source: De Mes et al. 2003, Kelley 2009, Affiliated

Engineers Inc 2014, Hamilton 2014, Matheri et al. 2016, Mutungwazi et al. 2017).

Type Feedstock HRT

(days)

Biogas

yield

Technology

Difficulty

Operational

mode

Continuously stirred tank

reactor (CSTR)

Slurry manure, abattoir waste and food

waste

Optimum: 3 % - 10 % total solids

Wet digestion

15 - 30 Good Medium Low-rate system

Lagoon digester Liquid (flush) manure

Optimum: 0.5 % - 3 % total solids

Wet digestion

20 - 200 Poor Low Passive system

Up-flow sludge blanket

(UASB)

Liquid waste

Optimum: low solids influent

Wet digestion

0.5 - 2 Good High High-rate system

Plug-flow digester Thick manure only

Optimum: 15 % - 20 %

Wet digestion

20 - 40 Poor Low Low-rate system

Fixed-film digester Liquid (Dilute waste streams)

Flush manure handling

Pit-recharge manure collection

Optimum: <5 % total solid waste

1-20 Good Medium High-rate system

In-situ cast concrete

digester (Puxin)

Sewage and food waste 30-40 Moderate

(compared to

other small

scale)

Low High-rate system



143

Table 4: Positive and negative characteristics of each digester type (Source: De Mes et al. 2003, Kelley 2009, Affiliated Engineers Inc 2014,

Hamilton 2014, Matheri et al. 2016, BiogasSA 2017, GreenCape 2017a, Mutungwazi et al. 2017, Steyn 2017, Tiepelt 2017).

Digester type

Positive characteristics Negative characteristics

Complete mix

digesters -

Continuously

stirred tank

reactor (CSTR)

Effective agitation; manure kept in suspension

Most popular AD technology worldwide; 80 % of digesters

installed in South Africa are CSTR;

high level of experience with CSTR digesters globally and in

South Africa

Ability to handle wide range of concentrations and influent total

solids; very successful for co-digestion

Wide range of application (abattoirs, food processing, fruit and

vegetables, manure)

Used with scrape/flush systems and dairy/swine systems

Good HRT (15 – 30), commonly holds 15 – 20 days’ worth of

manure and wastewater

Good HRT enables establishment of effective contact of bacteria

and substrate with high and consistent biogas production

Most effective and flexible technology; economically predictable

Consistent to manage; with medium degree of technical difficulty

Has to be heated

Poor biomass immobilisation

Mechanical mixing requirement

Digester size can be an issue at lower solids concentrations,

thus greater volume required thus larger digester

High capital cost

Need for periodic maintenance of mechanical parts of

digester

Lagoon digester Waste storage as well as waste water treatment system

Sludge can be stored for 20 years

Cheap and effective in reducing odours

Good for seasonal harvesting

Low tech difficulty

Longest HRT

No need for heating (depending on location)

Low capital requirements

Works well with single source substrate

Low initial maintenance

Methane production follows seasonal patterns with lowest

gas production;

Least controlled system

Life time maintenance on cover, but cover prone to damage

Solids/nutrient accumulation

Very costly to heat if required;

Gas leakage detected

High retention rate (20 – 200 days), slow solid conversion

No agitation, bacteria and liquid have limited contact

Periodic cleaning needed and maintenance of lagoon is

difficult;

Not effective with co-digestion

Often incomplete digestion and odour elimination



144

Digester type

Positive characteristics Negative characteristics

Up-flow sludge

blanket (UASB)

Effluent is often recycled to provide steady upward flow

Good biogas yield, with good HRT (30-60 days)

Simple design, easy construction and maintenance

Low operating cost; high removal efficiency

Moderate to low energy demand

Difficult to operate

Requires heating

High capital cost

Highly applicable to industrial waste and sewage

Plug-flow

digester

Simple design requiring easy installation and handling

Adaptable to extreme conditions at high altitudes with low

temperatures

Low capital cost;

reasonable retention time

Does not require mechanical mixing, reducing maintenance and

failure rates;

Works well with single source substrate

Works well with dairy manure and scrape system

No agitation; slow solid conversion;

Low biogas production

Primary feedstock is manure, limited success with co-

digestion;

Requires high solids manure (11-14 %)

Not compatible with sand bedding

15 % - 20 % solid content required may need extra added

material;

Constant volume, but produces biogas at a variable pressure

Fixed-film

digester

HRT can be <5 days, making for relatively small digesters

Short retention time with the ability to retain anaerobic

microorganisms within the digester irrespective of the short

retention time.

Easy construction

Moderate operation

High biogas yield

Need for periodic cleaning and replacement of the film

Plugging of the voids between supporting media is usually a

problem when high solids develop within the digester

Absence of uniform temperature distribution

Feed preparation should contain 1–3 % total solids

Some potential biogas is lost due to removing manure solids

Slow degradable solids must be removed before manure

enters digester which is time consuming

In-situ cast

concrete

digester (Puxin)

Easy to clean;

can be constructed from 60 to 1000m3

Gas produced under constant pressure

Variety of organic feedstocks

Ensures long term structural and functional integrity (solid

concrete structure)

Does not require a lot of people to operate

Household scale (too small for agricultural application,

loss in feedstock quality and not meeting energy

requirements)

Only suitable for installation in areas where the ground is

good enough for economic excavation

Biogas production limited to small gas appliances,

compared to gas yield of medium scale plants processing

larger volumes of agricultural waste

Periodic cleaning needed



145

3. Results and discussion

3.1 Analyses and interpretation of sustainable potential results according to hypotheses

3.1.1 Hypothetical calculations of sustainability potential scores (SPSs per digester type

per sustainable category factors (SCF)

Table 5: The format of the calculations of hypothetical SPSs of five digester types.

Sustainability potential score per digester type per sustainable category factors

Sustainability

category

Sustainable

Category

Factors

(SCF)

Digester type

Digester

A

Digester

B

Digester

C

Digester

D

Digester

E

Economic Technical factors 3 3 2 1 5

Fertiliser

production

2 3 1 1 5

Financial

requirements

4 2 2 1 4

Government

support

1 3 1 1 5

CEPa (20) 10 11 6 4 19

Social Job creation 2 5 3 2 4

Health benefits 2 5 2 3 5

Convenience and

access

6 5 1 1 5

Government

support

2 4 1 4 4

CSP (20) 12 19 7 10 18

Environmental GHG Mitigation 5 5 2 5 5

Waste

management

4 5 3 4 5

Renewable

resource

utilization

(Energy and

fertiliser)

3 4 2 5 5

Government

support

4 3 1 1 4

CEPb (20) 16 17 8 16 19

TOTAL sustainability potential

value (TSPV) (60) per digester

38 47 19 30 56

TOTAL sustainability potential

percentage (TSPP) per digester

(%)

63 % 78 % 32 % 50 % 93 %

Sustainability potential score

(SPS) (%/20) 3.2 3.9 1.6 2.5 4.7


146

Table 6: Hypothetical SPS and final SPC for each digester type.

Digester type Sustainability potential

score (SPS) (Table 5) Sustainability potential

category (SPC) (Table 2)

A 3.1 Average

B 3.9 Average

C 1.6 Poor

D 2.5 Low

E 4.7 Good

3.1.2 Interpretation of sustainable potential results

When analysing the data, it is important that the SPS is calculated to one decimal (Table 5),

as it can influence the SPC of the digester and will result in critical information regarding the

CEPa, CSP and CEPb values left disregarded. A SPS of 3.9 (for example digester B) is very

similar to a SPS of 4, indicating that the digester has good potential. However, when referring

to the definition of average potential (SPS 3–3.9), the digester shows moderate/fluctuating

sustainable potential; indicating a fluctuating difference in the CEPa, CSP and CEPb values,

resulting in the digester type not being classified as having “good sustainable potential”.

According to the definition of sustainability and sustainable potential (section 2.1.1), the

digester type should meet the requirements of all three pillars (economic (CEPa), social

(CSP) and environmental (CEPb)). In this case the CSP (19) and CEPb (17) values are

relatively high, whereas the CEPa (11) value is lower and identified as an outlier. Thus,

digester B would have a SPC of “average potential” stating that “Digester type shows

average potential due to an average sustainable potential score with moderate/fluctuating

economic, social, and environmental sustainable potential. Faces some challenges, with

reasonable room for improvement in a specific sustainable category (SC)/certain sustainable

category factors (SCF).”

To establish why digester B (for example) only has an average sustainable potential, SC

potential should be considered. To determine the sustainable potential of each SC, the

CEPa/CSP/CEPb values can be divided by four (as there are four SCFs). Then it is possible

to identify the SC with the lowest values. This can be addressed by improving the SPS of a

specific SC and improve the over-all SPS of the digester type. Table 7 shows how the SPC

for each SC of digester B is measured as an example, followed by how to interpret the

economic potential specifically for this digester type based on its hypothetical scores.


147

Table 7: Calculations based on the hypothetical results for Digester B (Table 5) to determine

the economic sustainable potential.

Sustainable Category (SC) Calculation SPS for each

SC respectively

Sustainable potential

category (SPC)

Sustainable economic potential

(CEPa/4SCF)

11/4 = 2.75 2.8

Low

Sustainable social potential

(CSP/4SCF)

19/4 = 4.75 4.8

Good

Sustainable environmental potential

(CEPb/4SCF)

17/4 = 4.25 4.3

Good

When measuring a specific SC, for example economic potential, the result for the specific SC

should then be paired with the corresponding SPC definition to determine the potential of that

specific SC.

By referring to section 2.1.1, the SPC for sustainable economic potential (2.8 – Low

potential) (Table 7) should be interpreted as “Digester type shows low potential due to a

sustainable potential score showing LOW ECONOMIC, sustainable potential. Faces many

challenges, with room for improvement in CERTAIN SUSTAINABLE CATEGORIES (SC).”

Thus to conclude this example, digester B shows low sustainable ECONOMIC potential

compared to the social and environmental SC’s, with good sustainable potential. The

potential of categories SPSC can also be applied to each SCF to determine specific

improvement within each SC. This can then be applied to improve the over-all SPS of a

digester type for future implementation.

3.1.3 Motivation of the Continuously Stirred Tank Reactor (CSTR) as the digester type

with the highest sustainable potential on farm-scale

The CSTR digester was identified with the highest sustainable potential for on-farm biogas

generation (Cavinato et al. 2000, Mata-Alvarez et al. 2000, De Mes et al. 2003, Szűcs et al.

2006, Jenkins et al. 2007, Hinken et al. 2008, Lutge 2010, Manyi-Loh et al. 2013, Affiliated

Engineers Inc 2014, Enitan 2014, Hamilton 2014, Shah et al. 2015, Zafar 2015, Culhane

2017, GreenCape 2017a, GreenCape 2017b, Mutungwazi et al. 2017, Steyn 2017, Tiepelt

2017).


148

This was based on the CSTR meeting most of the requirements (also see APPENDIX F) for

sustainable biogas digesters (De Mes et al. 2003, Szűcs et al. 2006, Jenkins et al. 2007,

Manyi-Loh et al. 2013, Affiliated Engineers Inc 2014, Enitan 2014, Hamilton 2014, Shah et

al. 2015, Zafar 2015,Culhane 2017, GreenCape 2017b).

3.1.4 Implementation factors for the on-farm CSTR digester.

The major expense in a biogas generation operation, specifically in South Africa, is the initial

capital investment and this is essentially the main reason why it is believed that biogas might

not have been economically viable on farms in 2010 (Lutge 2010). However, the trend in

setting sustainability goals and new agreements by South Africa and the United Nations (NT

2013, NT 2014, Ruffini 2014, SAGEN and SABIA 2016, Atkins 2017, GreenCape 2017b,

UNDP 2017) have led to numerous incentives to promote the industry especially on farms.

Realising that the initial capital investment for a biogas plant is high, with a fairly long

payback period of 5 to 8 years, BiogasSA is currently developing a practical and cost-

effective solution allowing farmers to participate in the actual construction of the plant

reducing costs considerably (BiogasSA 2017).

GreenCape (2017c) stated that the successful business cases are driven by a variety of models

regarding feedstock, utilisation of energy for heat and electricity and off-take products.

However, the success factors that these business cases have in common include energy

savings, waste management savings, robust systems with flexible feedstock and revenue from

multiple sources.


149

Table 8: Estimated comparative costs of proposed CSTR design plants for on-farm biogas

generation in South Africa done by BiogasSA and Botala Energy Solutions. (Sources:

BiogasSA 2017, Steyn 2017).

Output

scale

Feedstock type

(number of animals)

CSTR

digester

and size

Feedstock

(ton) (Steyn

2017)

Total cost

estimation

(15 %

accuracy)

(Steyn 2017)

Payback

period

(years)

(Steyn

2017)

Raw gas

only

Fruit and vegetable waste 50 x 40m 20 t day-1

7300 t.year-1

R3 590 000 5 – 8

60kW Dairy (300; 20 %

collection) and feedlot

manure (2000; 20 %

collection), and abattoir

(10.day-1) waste

30 x 50m 4 t.day-1 R2 920 000 7.5

60kW Dairy (300; 90 %

collection) and feedlot

manure (2000; 90 %

collection), and abattoir

(10.day-1) waste

38 x 50m 6 t.day-1 R3 820 000 7.5

80kW Fruit and vegetable waste 29 x 50m 8 t.day-1`

2920 t.year-1

R3 860 000 5 – 8

80kW Dairy cow manure

(16 000)

45 x 50m 64.9 t.day-1

23700 t. year-1

R6 680 000 6.5

100kW Layer chicken manure

(45 000)

43 x 50m 5 t.day-1,

13 600 t.year-1

R2 370 000 6

120 kW Dairy manure (900;

80 % collection)

38 x 50m 26 t.day-1 R4 920 000 4

150kW Layer chicken manure

(30 000)

47 x 50m 30 t.day -1

10900 t.year-1

R 11 280 000 4.5


150

Figure 2: Concept CSTR digester process with the highest sustainable potential for on-farm biogas generation with AD of agricultural waste.

(See APPENDIX G for layout and process flow. This diagram was constructed with the assistance of P. Steyn (Managing Director of Botala

Energy Solutions, South Africa) and M. du Toit (Architectural drafting)).



151

Conclusion

There is substantial opportunity in the agricultural sector to apply the available technologies

for biogas generation as a sustainable practice. Not only could it stimulate the much-desired

sustainable rural revitalisation and address energy poverty, but the highest potential of AD

implementation in South Africa is reported to be on farm-scale.

At present, there is no decision-making tool to identify the specific digester type that would

demonstrate the most sustainable potential on farms, as there are too many variables such as

feedstock availability, legislation, willingness, climatic factors, water availability, and

availability of skills and experience, which complicate the implementation of biogas

generation. Therefore, a generic model was developed to determine the digester type with the

highest sustainable potential according to the specific requirements of a farm.

The generic model is embedded in the concept of sustainability and is based on scoring

digester types according to the three categories of sustainability: economic, social and

environmental. This presents a unique opportunity to address all three pillars of sustainability

according to factors that define each of the sustainability categories. The final numeric value

is used to determine the most suitable digester type on site.

In this study, the selection of a digester type was complicated, as it was necessary to integrate

the criteria for efficiency and feasibility, as well as the requirements for sustainability. The

continuously stirred tank reactor (CSTR) demonstrated the highest potential as sustainable

agricultural practice when characteristics were compared against other digester types.

However, the validation of this choice was not possible in the scope of this study. Future

studies are recommended for application of the generic model on different farms to validate

the sustainable potential of different agricultural biogas digester types, and it is recommended

that the CSTR digester should be included.


152

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162

GENERAL CONCLUSION

New and innovative ways that will enable the agricultural community to farm in a more

sustainable manner could contribute to improving South Africa’s sustainability standing in

relation to other sub-Saharan countries and the world. This potential could be realised

specifically with regards to the agricultural waste management sector and in the secure

supply of renewable energy, as biogas generation is one of the few technologies that

addresses both these issues and that has the potential to improve sustainability on an

economic, social and environmental basis. Biogas generation as an alternative renewable

source of energy could potentially mitigate the effects of climate change, enable the country

to meet peak electricity demands as it is not dependent on resources like wind or water, and

can be implemented on any site where waste feedstock is readily available.

By investigating the biogas digester industry in South Africa, it was found that the interest in

the development of medium and commercial-scale biogas digesters can be attributed to

opportunities that the biogas industry offers in terms of job creation, energy provision, carbon

mitigation, organic fertiliser production and waste management. The study confirmed that,

while the biogas digester industry in South Africa is currently faced with numerous

challenges in terms of renewable energy generation and supply, e.g. a lack of government

support, financial commitments involved in its development, skills shortages, ethical

challenges, limited water resources and sustainable access to waste as a biomass source,

innovative enablers exist that can promote the growth of the industry. By applying enabling

factors such as streamlining EIA processes and licencing, biogas generation could provide tax

relief through the anticipated implementation of carbon tax, and offer inventive solutions for

waste management, while delivering ecosystem services and improved water and soil quality

which may result in increased in food production.

Substantial opportunity exists, also in the agricultural sector, to apply the available

technologies for biogas generation as a sustainable practice. Not only could it stimulate the

much-desired sustainable rural revitalisation and address energy poverty, but it is believed

that the highest potential of anaerobic digestion implementation in South Africa is on farm


163

scale. Here, farms may benefit through the generation of electricity, as well as costs savings

associated with organic waste treatment, storage and transportation.

This study attempted to further define the potential of farm-scale biogas generation as a

sustainable agricultural practice in South Africa through interaction with the farming

community. Although substantial understanding of sustainability and the economic potential

of biogas generation exists, a lack of knowledge, expertise, financial support and incentives

were found to be obstacles in the practical implementation of biogas generation limiting the

potential in rural areas. Limited knowledge exists about possible rebates in terms of

generating renewable energy and the perception of the farming community is that no

effective and sufficient platform for government compensation towards a farmer for reducing

GHG emissions exist, constituting too big a financial investment/risk. The availability of

information, knowledge and skills regarding this industry affects its economic, social and

environmental potential. Addressing this issue specifically would create significant

opportunities to develop the potential of this industry in the agricultural sector.

This notion supports recent literature and expert opinions in the field that South Africa lacks

the operational experience and skills that is needed to optimise the country’s biogas potential.

Developing the economic potential of biogas generation will require wide-scale knowledge

transfer about the financial opportunities that it presents to supply for energy and heat

demands of agricultural operations and the role that the availability of feedstocks play in the

realisation of this potential. The availability of financial support, whether in the form of joint

ventures between developers and farmers, or as incentives or rebates applied for the

generation of renewable energy, will enable the industry to grow. This will allow the farming

community to overcome the financial hindrances and perceived risks that currently prevents

them from pursuing new technology.

By further investigating the sustainable potential of specific biogas digesters applicable as

sustainable agricultural practices, it was found that it is not possible to identify one specific

biogas digester type that would demonstrate the highest potential in an agricultural

sustainability context, as there are too many variables. It thus became apparent that the choice

and implementation of a biogas digester on a farm should be site-specific to be feasible.

At present, there is no decision-making tool to identify the specific digester type that would

demonstrate the most sustainable potential on farms. Therefore, a generic model was


164

developed to determine the digester type with the highest sustainable potential according to

the specific requirements of a farm. The generic model is embedded in the concept of

sustainability and is based on scoring digester types according to the three categories of

sustainability: economic, social and environmental. This presents a unique opportunity to

address all three pillars of sustainability according to factors that define each of the

sustainability categories. The final numeric value is used to determine the most suitable

digester type on site. In this study, the selection of a digester type was complicated, as it was

necessary to integrate the criteria for efficiency and feasibility, as well as the requirements for

sustainability. The continuously stirred tank reactor (CSTR) demonstrated the highest

potential as sustainable agricultural practice when characteristics were compared against

other digester types. However, the validation of this choice was not possible in the scope of

this study. Future studies are recommended for application of the generic model on different

farms to validate the sustainable potential of different agricultural biogas digester types, and

it is recommended that the CSTR digester should be included.

The study also clarified that the major expense in a biogas generation operation, specifically

in South Africa, is the initial capital investment and this is essentially the main reason biogas

generation on farm-scale has not been viable till now. Taking the current Eskom tariff

together with the escalation of the Eskom tariff over the next five years into account, biogas

plants may only break even after approximately 4-5 years, and start to pay back after 7-10

years, making it not immediately viable on a farm-scale if the motivation to implement

biogas digesters is primarily based on pay-back returns for the generation of electricity.

However, by applying this technology to generate energy and heat for own use on site, and

viewing it as a mechanism to save costs on waste management and fertiliser supplies, biogas

generation could be implemented as a sustainable agricultural practice contributing not only

to rural revitalisation but also to environmental health and subsequent food production.

To conclude, although numerous challenges impede the potential of biogas generation in

South Africa at present, the potential of biogas generation to contribute to sustainable

development was quantified and it was found that there is substantial opportunity for

government intervention as a means to promote sustainability, not only on farm-scale but also

to the benefit of the country as a whole.


165

APPENDICES

APPENDIX A: The Global Sustainable Development Goals, United Nations Development Programme (Source: UNDP 2017)



166

APPENDIX B: The plant capacity and scale of biogas digesters in use in South Africa (Source: Smith 2011, SAGEN and SABIA 2016,

BiogasSA 2017, Mutungwazi et al. 2017, Tiepelt 2017).

Scale Location Energy

generated

Use of energy Tonnage and

feedstock required

Types installed South African sites

(developers)

Large abattoir feedlot

agricultural

processing

WWTW

>1 MW Self-consumption

heating or

electricity

generation

(fed into the grid)

15-150 t of MSW per

year:

manure/abattoir/

WWTW (typical

feedstock)

Lagoon type digesters

Large-scale mixed-waste CSTR

AD system

Bronkhorstspruit

(Bio2Watt)

Uilenkraal

(CAE & Morgan)

Abattoir Springs

(BiogasSA)

Medium farms

communities

breweries

restaurants

schools

>30 kW

and

<1 MW

Self-consumption,

heating or

electricity

generation

(possibility to feed

into grid)

2-15 t of MSW per

year: manure /

agricultural / abattoir

/ sewage (typical

feedstock)

Lagoon digester, plug-flow digester,

complete mix digesters, up-flow

sludge blanket digester (UASB)

Jan Kempdorp

(Ibert, WEC)

Small households

small farms

<30 kW Self-consumption,

heating or

electricity

generation

0,1-2 t of MSW per

year: manure /

sewage (typical

feedstock)


digester (Puxin), brick and mortar

fixed-dome digester, floating dome

digester, plug-flow digester

Waste to Energy

Programme

(SANEDI, Agama

& BiogasSA)

Rural/

domestic

off- grid, rural

communities

individual

households

low income

households

<10 kW Supply energy for

cooking, lighting or

sanitation in rural

residential areas,

e.g. household with

two cows

<1 t of MSW per

year: manure or

sewage (typical

feedstock)


digester (Puxin), brick and mortar

fixed-dome digester, floating dome

digester, DIY biobag digester kit,

LGM rotor moulded in-ground

household digester,

EZ-Digester, African green energy

technologies (AGET) 10m3 and AGET

2.5m3 portable digester

EZ-digester

(BiogasSA)



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APPENDIX C: Survey 1 (S1) – Famers without biogas digesters

Evaluating the sustainable potential of Biogas generation in South Africa

Surveys for farmers without biogas digesters

GP Jordaan [email protected]

MSc Sustainable Agriculture


Name:

Name of Farm:

Location:

*Please highlight selected answer:

(Yes/No)

(a) I think this is the right answer

(b) I think this is the wrong answer

*Please type answer in red where applicable.

Sustainability

1) Have you ever heard of the term sustainability? (Yes/No)

2) Do the terms “organic” and the “sustainability” mean the same thing to you? (Yes/

No)

3) How would you define sustainability with regards to the following definition

“Process of utilizing and living within the limits of available physical, natural and

social resources in ways that promote……?

a. social sustainability.

b. ecological sustainability

c. economic sustainability.

d. A and B

e. B and C

f. A and C


mailto:[email protected]

168

g. A, B and C

4) Sustainability takes into account ecology, economy and social sustainability?

(True/False)

5) Do you feel there is a need for farmers to incorporate more sustainable practices in

South Africa? (Yes/No)

6) Do you feel that there is a consumer’s demand for incorporate more sustainable

practices in South Africa?(Yes/No)

7) Do you feel the electricity crisis in South Africa affects your agricultural practice?

(Yes/No)

8) Do you feel that generating environmentally friendly electricity promotes

sustainability for a country? (Yes/No)

9) Do you think you are living in a sustainable manner? (Yes/No/ Not yet, but I am

trying)

Biogas digesters

1) Do you have a working biogas digester on your farm? (Yes/No)

2) Have you ever heard of a biogas digester? (Yes/No)

3) Have you ever worked with a biogas digester before? (Yes/No)

4) Are you aware of climate change? (Yes/No)

5) Are you aware of any negative influences that climate change might have on your

agricultural practices? (Yes/No);

If Yes please list these influences below:

…………………………………………………………………………………………

………………………………………………..…………………………………………

……………………………………..

6) Did you know that Methane (CH4) and Carbon dioxide (CO2) are some of the biggest

contributors towards climate change? (Yes/No)

7) Are you aware of the fact that agricultural activities produce unwanted human derived

gasses such as Methane (CH4) and Carbon dioxide (CO2) in large uncontrollable

quantities? (Yes/No)


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8) The global population is growing (expected 9billion in 2050), yet people need to eat;

Do you think it is too late for farmers to farm more sustainably? (Yes/No)

9) Define what you think a biogas digesters is, by choosing one option below:

a. Food digester system in your kitchen which works on biogas to reduce

Methane (CH4) in domestic households.

b. Simple process which facilitates the natural anaerobic decomposition of

organic material to catch up Carbon Dioxide (CO2) and Methane (CH4), and

uses the methane to generate energy in the form of gas electricity.

c. Machine which makes use of biological gas in the form of Methane (CH4) to

drive the engine of a vehicle.

d. Large wind turbines which generate biogas to contribute towards more

sustainable living and reduce carbon dioxide (CO2) and Methane (CH4)

e. I have no idea what a biogas digester is.

10) What agricultural activities do you practice on the farm?

(…………………………………………………………………………………………

………………………………………...)

11) How do you dispose of your agricultural waste?

-

-

12) What is the cost of total waste disposed per month? (…………………………………)

13) What are your major forms of agricultural waste on the farm? You may tick more

than one option.

a. Organic plant waste

b. Plastics

c. Animal Manure

d. Waste water

e. Animal body part waste

f. Other

14) Are you aware of ways to get rid of waste on the farm by using biological methods?

(Yes/No)


170

15) Are you aware of the fact that animal waste, organic plant matter and abattoir waste

can be used to generate methane which can be used as gas for cooking and heating

and to generate electricity? (Yes/No)

16) Do you generate your own electricity on the farm (Yes/No); If yes do you use

(solar/wind/hydro/biogas) and do you get any rebates from the government for

generating environmentally friendly electricity (Yes/No)?

17) Are you connected to the Eskom electricity grid? (Yes/No)

18) Do you ever struggle with power cuts? (Yes/No); If yes, does it influence your

agricultural practices, ultimately leading to financial losses (Yes/No)?

19) How much money do you spend on Electricity per month on the farm?

(…………………….)

20) Is electricity a major expense on the farm? (Yes/No)

21) Is fertiliser a major expense on the farm? (Yes/No)

22) Do you make use of raw sewage sludge from Waste Water Treatment Works as a soil

conditioner for soil preparation? (Yes/No)

23) Do you make use of any other raw form of manure or sludge as soil conditioner or

soil preparation? (Yes/No)

24) What type of energy source do your farm workers use?

a. Electricity only

b. Gas only

c. Fuel wood only

d. A and B

e. B and C

f. A and C

g. A,B and C

25) What are the main reasons why you do not invest in generating your own electricity?

a. It is too expensive to install a new electricity generating process

b. The technology will not work on my farm

c. It is easier to stick to what we know, Eskom.

d. It is too time consuming

e. I do not now enough.

26) From the benefits regarding biogas generation listed below, select the benefits that

you were not aware of:

a. Reduction of waste (over-capacitated landfills)


171

b. Heat and electricity generation

c. Health benefits

d. Alleviate poverty

e. Methane gas production (commercial or domestic use)

f. Utilization of methane

g. GHG (Greenhouse Gas) emission grants

h. Growth of potential fertiliser industry

i. Improve crop quality and soil fertility

j. Growth of the green economy (job creation/skills development)

Notes and comments:

Thank you for your time and effort.

Your input is of great value towards my study.


172

APPENDIX D: Survey 2 (S2) – Farmers with biogas digester

Evaluating the sustainable potential of biogas generation in South Africa

Surveys for farmers with biogas digesters

GP Jordaan [email protected]

MSc Sustainable Agriculture


Name:

Name of Farm:

Location:

*Please highlight selected answer:

(Yes/No)

(c) I think this is the right answer

(d) I think this is the wrong answer

*Please type answer in red where applicable.

Sustainability

10) Have you ever heard of the term sustainability? (Yes/No)

11) Do the terms “organic” and the “sustainability” mean the same thing to you? (Yes/

No)

12) How would you define sustainability with regards to the following definition

“Process of utilizing and living within the limits of available physical, natural and

social resources in ways that promote……?

a. social sustainability.

b. ecological sustainability

c. economic sustainability.

d. A and B

e. B and C

f. A and C


mailto:[email protected]

173

g. A, B and C

13) Sustainability takes into account ecology, economy and social sustainability. True or

false?

14) From a farmer’s perspective, do you feel there is a need for farmers to incorporate

more sustainable practices in South Africa? (Yes/No)

15) Do you feel that there is a consumer’s demand for incorporate more sustainable

practices in South Africa?(Yes/No)

16) Do you feel the electricity crisis in South Africa affects your agricultural practice?

(Yes/No)

17) Do you feel that generating environmentally friendly promotes sustainability for a

country? (Yes/No)

18) Do you think you are living in a sustainable manner? (Yes/No/ Not yet, but I am

trying)

Biogas digesters

1. Where did you hear about biogas digesters?

a. I read about it online

b. By a friend/colleague/family

c. South African biogas digester company

d. Heard about it in another country

e. Other

2. What is the primary type of farming on the farm?

(…………………………………………………….)

3. What is the size of the allocated area for agriculture?

(…………………………………………….)

4. What type of biogas digester do you have on the farm?

(…………………………………………………….)

5. When did you install the biogas digester? (…………….…)

6. Which company did the installation? (………………../self-installation)

7. How many litres of water is used on the farm per month?

(…………………………………………………)


174

8. How many litres of water does the biogas digester use per month?

(…………………………………..)

9. In terms of (kW)/(MW), what is the size of your biogas digester?

(…………………………...)

10. How much was the start-up cost for your digester/plant?

(………………………………………………….)

11. Did you make use of any subsidies or incentives with regards to the installation cost

of the digester? (Yes/no); If yes, was this government based support?

12. What is the major raw material source used as feedstock?

(…………………………………………..)

13. What is the amount of feedstock (tonnage) used per month?

(……………………………)

14. I am using my biogas digester for (Methane gas use/Electricity generation/Soil

conditioner/All of the above/non-of the above)

15. Do you make use of all of the biogas produced? (yes/no); If no, what do you do with

the excess biogas? (………………………..)

16. Do you generate your own electricity on the farm (Yes/No); If yes do you use

(solar/wind/hydro/biogas) and do you get any rebates from the government for

generating environmentally friendly electricity (Yes/No)? If Yes, for which type of

method do you receive rebates (solar/wind/hydro/biogas)?

17. Do you have a dedicated operator for the biogas digester? (Yes/No)

18. Do you operate the digester on your own? (Yes/No)

19. How many people are employed to work on the biogas digesters? (…………….)

20. How did you dispose your waste before making use of a biogas digester?

21. Is it financially viable to operate a biogas digester on your farm? (Yes/Not at the

moment but potentially in the future/No)

22. Do you feel it contributes in terms of sustainability (Yes/No)

23. Do you store any of the products from the biogas digester? (Yes/No). If yes,

a. What type of product do you store? (gas / digestate/methane)

b. Describe the type of product chosen in question 20 a?


175

c. What method of storage do you use?

(…..………………………………………………………………..)

24. Do the farm workers get access to the products of the biogas digester? (Yes/No); If

yes, what type/s of product/s do the farm workers get access to?

(Electricity/Biogas/Soil conditioner)

25. Do you feel that by installing a biogas digester it has created new jobs on the farms,

thus promoting social sustainability? (Yes/No)

26. Do you feel there is potential for small medium biogas digesters (<30Kw and >1MW)

in South Africa? (Yes/No)

a. Why?

27. Do you feel there is potential for large scale (<1MW) biogas digesters in South

Africa? (Yes/No)

a. Why?

28. What type of biogas digester system would you recommend as the most suitable farm

scale biogas digester system for South Africa?

-

29. List the major benefits are there for you in terms of operating biogas digesters on the

farm?

-

-

-

-

30. List one major hindrance regarding the operation of your biogas digester system?

-


176

31. In terms of policy and legislation, do you find that there are any hindrances from the

government’s side? (Yes/No).

If yes, list these hindrances?

-

-

-

-

32. Do you think there is a lack of education regarding biogas digester systems? (Yes/No)

33. Do you think there is a lack of skill development in the biogas digester industry?

(Yes/No)

34. What is your opinion on the fact that electricity generated by biogas digester systems

cannot be connected directly to the grid, where wind and solar energy are able to

connect to the grid?

35. Are you connected to the Eskom electricity grid? (Yes/No)

36. How much money do you save by using a biogas digester?

(……………………………………/none)

37. Do you ever struggle with power cuts? (Yes/No); If yes, does it influence your

agricultural practices, ultimately leading to financial losses (Yes/No)?

38. How much money do you spend on electricity per month on the farm?

(………………………..)

39. Is electricity a major expense on the farm? (Yes/No)

40. Is fertiliser a major expense on the farm? (Yes/No)

41. Do you make use of any other raw form of manure or Waste Water Treatment sludge

as soil conditioner or in soil preparation? (Yes/No)

42. Do you make use of your own digestate as soil conditioner/compost? (Yes/No)

43. Do you sell your digestate for fertiliser production? (Yes/No)

44. What are the main reasons why other people do not invest in generating their own

electricity by using biogas digester systems?

k. It is too expensive to install a new electricity generating process

l. The technology will not work on their specific farm

m. It is easier to stick to what we know, Eskom.


177

n. It is too time consuming

o. People are uneducated in the field.

p. Other

(…………………………………………………………………………………

……………………………………………)

Notes and comments:

Thank you for your time and effort.

Your input is of great value towards my study.


178

APPENDIX E: Digester types description with specific reference to potential on-farm

biogas generation (Paper 3).

The following digester types where identified as having sustainable potential with regards to

biogas generation in the agricultural sector in South Africa: CSTR (continuously stirred tank

reactor), lagoon digester, up-flow sludge blanket (UASB), plug-flow digester and fixed-film

digester. Mutungwazi et al. (2017) found the in-situ cast concrete digester (Puxin) to be the

most suitable (not necessarily having the highest sustainable potential) small-scale design for

installation in the South African context.

Complete mix digester - Continuously stirred tank reactor (CSTR)

Complete mix digester is a collective term for hardware that contains, heats and continuously

or intermittently stirs/mixes an active mass of micro-organisms inside the digester (Figure 1)

(Hamilton 2014). Incoming liquid displaces volume in the digester, and an equal amount of

liquid flows out, together with methanogens. Digestion may take place in more than one tank

(acid-formers break down manure in one tank, and methanogens convert organic acids to

biogas in a second tank). Biogas production is maintained by adjusting volume so that liquids

remain in the digester for 20 days to 30 days, but retention can be shorter for thermophilic

systems (Hamilton 2014, Mutungwazi et al. 2017). Manure is typically heated to maintain a

mesophilic or thermophilic environment, often using recovered heat from the biogas burner;

these digesters work best when manure contains 3 to 6 % solids (Affiliated Engineers Inc

2014); lower solids mean greater volume, requiring a larger digester to retain the microbes

for 20 days to 30 days (Hamilton 2014).

There are three known types of complete mixed digesters: continuously stirred tank reactor

(CSTR); completely mixed flow reactor (CMF) and continuous-flow stirred tank (CFST)

(Kelley 2009). A CSTR digester has a sealed, cylindrical concrete or steel tank, where

feedstock is mechanically kept in suspension by a motor-driven impeller, pump, or other

device (Affiliated Engineers Inc 2014). The typical sources of feedstock for CSTR digesters

are abattoirs, food processing plants, fruit/vegetable packaging and poultry, pig and dairy

farms (Hamilton 2014).


179

Figure 1 Schematic drawing of a complete mix digester (Source: Hamilton 2014).

Lagoon digester

The lagoon digester has an impermeable cover that contains and traps biogas as anaerobic

decomposition of the waste progresses, and while it stores waste it also acts as a waste

treatment system. It has two cells, both of which are needed for the system to work at its best

(Figure 2) (Affiliated Engineers Inc 2014, Hamilton 2014, Mutungwazi et al. 2017). While

the first cell is covered, the second cell is uncovered and the liquid level in the second cell

rises and falls to create storage while the level on the first cell remains constant to enable

decomposition (Hamilton 2014). Lagoon digesters are not heated and are sometimes called

ambient temperature digesters as it follow seasonal patterns. While a covered lagoon in the

tropics will produce gas all year, methane production drops when temperatures fall below

20°C (Hamilton 2014, Steyn 2017). The methane producing organisms remain in in the

covered lagoon for as long as sludge can be stored (which could be up to 20 years) effectively

retaining many fertiliser nutrients, particularly phosphorus, in the lagoon (Hamilton 2014).

Lagoon covered digesters in South Africa are relatively cheap compared to other on-farm

digesters (GreenCape 2017a, Steyn 2017).

Figure 2: Schematic drawing of a lagoon digester (Source: Hamilton 2014)


180

Up-flow sludge blanket (UASB)

In an UASB reactor (Figure 3), the influent enters through the bottom of the reactor, enabling

contact between the accumulation of microbial biomass in the sludge bed and blanket with

the influent (Abbasi and Abbasi 2012, Enitan 2014). USAB digesters is a suspended media

digester where microorganisms are suspended in a constant upward flow of liquid, enabling

them to form biofilms around the larger particles, and causing the methanogens to stay in the

digester (Hamilton 2014).

As UASB reactors are highly dependent on its granular sludge during wastewater treatment

to effectively transform organic matter to biogas (Batstone et al. 2002, Liu et al. 2003, Enitan

2014), some designs include other supporting media, such as sand for microbes to form a

biofilm on (Hamilton 2014). These are called fluidized-bed digesters, and flow is adjusted to

allow smaller particles to wash out, while allowing larger ones to remain in the digester

(Hamilton 2014).

Figure 3: Schematic drawing of an Up-flow sludge blanket (UASB) digester (Source:

Hamilton 2014).


181

Plug-flow digester

The plug-flow digester (Figure 4) is based on a concept similar to a complete mix digester

with equal amounts of substrate/manure flowing into and out of the digester (Hamilton 2014,

Mutungwazi et al. 2017). The digester includes a long and narrow tank with an average width

to length ratio of 1:5 (Tervahauta et al. 2014), with the inlet and outlet of the digester set at

opposite ends above the ground, and part of the digester located underground at an inclined

position that enables a two-phase system where methanogenesis and acidogenesis is

separated longitudinally (Mutungwazi et al. 2017). As no lengthwise mixing of the substrate

from inlet to outlet takes place, the substrate flows as a plug and it is thick enough to keep

particles from settling to the bottom (Hamilton 2014, Mutungwazi et al. 2017).

The digester can be covered with a roof to avoid temperature fluctuations and keep the

process temperature (Mutungwazi et al. 2017). While the plug-flow digester design, first used

in South Africa in 1957, produces biogas at a variable pressure, it has a constant volume

(Ghosh and Bhattacherjee 2013, Mutungwazi et al. 2017).

Figure 4: Schematic drawing of a mixed plug-flow digester (Source: Hamilton 2014).

Fixed-film digester

The fixed-film digester (Figure 5) consists of a tank where methane-forming microorganisms

grow on supporting media such as wood chips or small plastic rings filling a digestion

column, and are also known as attached growth digesters or anaerobic filters (Hamilton

2014,Mutungwazi et al. 2017).


182

As the waste manure passes through the media, biogas is produced (Hamilton 2014). The

media supports a thin layer of anaerobic bacteria termed bio-film giving rise to the name of

the digester (Ghosh and Bhattacherjee 2013). The immobilisation of the bacteria as a bio-film

prevents the washout of slower growing cells and provides biomass retention independent of

HRT (Mutungwazi et al. 2017).

A solid separator is needed to remove particles from the manure before feeding it to the

digester (Hamilton 2014). Like covered lagoon digesters, fixed-film digesters are best suited

for diluted waste streams and can be used for both dairy and dairy and swine wastes

(Mutungwazi et al. 2017).

Figure 5: Schematic drawing of a fixed film digester (Source: Hamilton 2014).

In-situ cast concrete digester (Puxin)

The in-situ cast concrete (Puxin) digester is a hydraulic household-scale digester to treat

sewage and food wastes, and was designed to solve the technical problems that were

experienced with traditional fixed and floating-dome digesters (BiogasSA 2017). BiogasSA

is the sole licensee for South Africa of the Shenzhen Puxin Science and Technology

Company (Puxin) of China (BiogasSA 2017).

The Puxin is constructed by casting concrete around small bolted steel panels that is stacked

in the form of an igloo to form the digester (Mutungwazi et al. 2017) (Figure 6), and has a

plastic fibre gas holder, neck and belly, and an inlet and outlet pit (BiogasSA 2017,

Mutungwazi et al. 2017). The entire digester is flooded with water at the same level, and the


183

decay of organic matter takes place under water, creating optimal conditions for AD and the

production of methane (Shenzhen Puxin Sci. Tech. Co. Ltd 2015, BiogasSA 2017,

Mutungwazi et al. 2017).

The gas produced is collected in the dome, and as the volume of gas increases, it shifts the

water downwards ensuing in an upward pressure on the gas due to the equal and opposite

reaction of the displaced water, ensuring in turn that the collected biogas in the dome is

always under constant pressure of up to 8 kPa - a major advantage for running gas appliances

(Shenzhen Puxin Sci. Tech. Co. Ltd 2015, BiogasSA 2017, Mutungwazi et al. 2017).

The light weight Puxin digester is easy to clean hence any type of organic material can be

used as feedstock (Shenzhen Puxin Sci. Tech. Co. Ltd 2015, BiogasSA 2017, Mutungwazi et

al. 2017).

Figure 6: Schematic drawing of an in-situ cast concrete digester (Puxin) (Source:

Mutungwazi et al. 2017).


184

APPENDIX F: Biogas generation requirements in the agricultural context matched to

the characteristics of the CSTR digester (Paper 3).

Co-digestion capabilities

The CSTR digester is not limited to one source of feedstock but able to digest a wide range of

influent total solids and concentrations, and a variety of organic matter, either alone or

through co-digestion (Affiliated Engineers Inc 2014, Enitan 2014, Hamilton 2014, Shah et al.

2015, Culhane 2017). The co-digestion capabilities of the CSTR digester makes it more

economically viable as a variety of agricultural waste streams can be used as feedstock on a

single farm; alternatively it can be implemented as a community-based plant making offering

the opportunity to farmers to process crop biomass together with animal manures, which is

the largest agricultural waste stream (De Mes et al. 2003, Zafar 2015, GreenCape 2017b).

Co-digestion promotes reactor efficiency and dilutes the inhibitory effects of substances,

improves microbial diversity and synergy (which plays an essential role in methanogenesis),

balances the micro and macronutrients, supplies missing nutrients from co-substrates such as

manures, and increases the methane yields per unit of digester volume (Cavinto et al. 2000,

Mata-Alvarez et al. 2000, De Mes et al. 2003, Hinken et al. 2008, Shah et al. 2015). Studies

have also found that biogas production per digester volume can be increased by operating the

digesters at a higher solids concentration (Zafar 2015), promoting the fact that CSTR

digesters are able to work over wide range of influent total solids (Hamilton 2014), while the

addition of plant material with high carbon content balances the carbon to nitrogen (C/N)

ratio of the feedstock, thereby decreasing the risk of ammonia inhibition (Zafar 2015).

Ability to use animal manure

The ability of CSTR digesters to use animal manure ensures the safe reuse and transformation

of waste into valuable materials and energy (Manyi-Loh et al. 2013). This decomposition of

animal manure that occurs within a confined area contributes to pollution control as it

destroys pathogens by reducing the microbial load to a level which could be safely handled

by humans (Jenkins et al. 2007).


185

Reasonable HRT

Compared to the other digesters, CSTR digesters have a reasonable HRT of approximately 15

to 30 days, increasing the contact time of wastewater with the sludge, and in this way

improving the effluent quality and biogas production rate (Szűcs et al. 2006, Enitan 2014).

Ability to withstand temperature fluctuations

Steyn (2017) suggests that in terms of seasonal temperature fluctuations in South Africa, a

plug-flow or lagoon digester is not recommended as a high sustainable potential option, as

winter temperatures constrain the digestion process. In comparison the CSTR is a heated

system ensuring constant temperatures at which AD can take place.

Availability of expertise and technology

The CSTR digester design is proven to be the most commonly used and successful anaerobic

digestion technology worldwide (Affiliated Engineers Inc 2014) and accounts for up to up to

80 % of digesters installed in South Africa (Mutungwazi et al. 2017), and 90 % of newly

installed wet digesters (Shah et al. 2015). This situation has created numerous opportunities

worldwide and in South Africa to build expertise and understanding of this particular

technology (Steyn 2017).

Ease of management

The CSTR digester design is regarded as having the highest potential in terms of farm-scale

implementation in South Africa (GreenCape 2017a, Steyn 2017, Tiepelt 2017) as it is

economically more predictable and consistent to manage (Lutge 2010, Steyn 2017).


186

APPENDIX G: CSTR digester layout and process flow; maintenance and development

(Paper 3: Figure 2).

Layout

Figure 1 shows the key components in the biogas plant: (1) mixing tank, (2) digestion tank,

(3) co-generation unit, (4) co-generation unit and electricity distribution system, (5) gas

treatment unit, (6) control system, (7) solid bio-fertiliser production, (8) lagoon effluent

storing and handling, (9) solid fertiliser packing line and (10) safety flame heat exchange

unit. The material flow includes biomass and organic waste as inputs, and electricity, organic

fertiliser and heat/hot water as outputs. The biogas plant will produce methane gas, which

will be converted into electricity and heat or hot water through a generator. The proposed

simultaneous use of both electricity and heat in this model opens a sustainable pathway to

reduce extra costs for heating and partial powering of mechanical mixers (GreenCape 2017a,

Tiepelt 2017). It is estimated that approximately 90 % of the organic input will come out as

enriched liquid fertiliser.

Input

One of the distinct advantages of a biogas plant is its ability to be located anywhere where

waste feedstock is available enabling it to contribute significantly to efficient waste

management (Biogas 2013, Msibi 2015, SAGEN and SABIA 2016). This makes it

particularly suitable for rural areas as the agriculture sector generates mainly organic waste

that could be used as feedstock (GreenCape 2016, GreenCape 2017b).

Feedstock can be cow, chicken or pig manure, food waste including oil, fat, fruit and

vegetable wastes, all components of slaughterhouse waste, any plant material (except

excessive amounts of wood) and human sewage (Enitan 2014, Hamilton 2014, Shah et al.

2015, Mutungwazi et al. 2017, Steyn 2017). Each type of feedstock should be suitably

processed to allow maximum efficiency of the bacterial digestion inside the tank. When

feedstock with a very low moisture content is used, fresh water/reused liquid in equal

quantities will have to be added (Steyn 2017).

Water scarcity in South Africa should not be seen as a limiting factor as up to 80 % of the

liquid can be reused depending of the type of feedstock, reducing the water requirements of a


187

digester substantially (Morales-Polo and del Mar Cledera-Castro 2016, Bansalet et al. 2017,

Tiepelt 2017). Reutilising the liquid digestate also has its benefits as the temperature of

reused digestate is higher and the warmer water creates a more suitable micro habitat for

digestion (Morales-Polo and del Mar Cledera-Castro 2016, Bansalet et al. 2017, Tiepelt

2017). Each type of feedstock has different digestion characteristics thus requiring different

tank sizes and generates different gas yields per tonne, supporting to the site-specific

approach (Lutge 2010, GreenCape 2017b, GreenCape 2017c, Mutungwazi et al. 2017, Steyn

2017).

Output of the process (biogas, heat and electricity generation)

The gas produced by the anaerobic decomposition process in the digesters is extracted on a

continuous basis into the gas treatment unit. The gas is collected from the top of the tank and

treated to allow it to be used as a fuel source in various ways. The gas at this stage comprises

approximately 60 % to 75 % CH4 (methane) and various other components (De Mes et al.

2003, Shah et al. 2014). The unwanted sulphurous (H2S) component in the gas is removed

and excess moisture is taken out of the gas stream. H2S is removed by a standard air-dosing

treatment into the digester head-space which causes sulphur-eating bacteria to consume the

H2S gas (Krayzelova et al. 2015). H2S gas formation can also be very effectively eliminated

by adding iron chloride solution into the digester mix tank (Kapdi et al. 2005). These

components must be removed to protect gas burning equipment from and other stainless steel

parts of the generator from corrosion (ISSF 2012).

Once the gas is cleaned it can be used as fuel for a standard internal combustion engine

driven generator to produce electricity or gas for heating and cooking appliances, hot water

boilers and household geysers (Mihic 2004, Steyn 2017, Tiepelt 2017). Operating the

generator at a constant output of 90 % of the peak power ensures full fuel efficiency and

energy production (Steyn 2017). The excess heat from the generator exhaust fumes can be

collected by an integrated heat recovery system (CHP) to produce steam or hot water for

general heating purposes (Naegele et al. 2012, Ahmed 2014, Steyn 2017). The total heat

energy contained in the hot water is up to 130 % of the total electrical energy produced by the

generator and the hot water is regarded as a valuable asset and energy source that should be

further applied to increase the energy savings potential of the plant (Naegele et al. 2012,

Steyn 2017). For electrical generation the correct generator size is selected to optimise the


188

use of the generator and to supply in the maximum power demand of the specific operation.

Depending on funds available, multiple smaller generators can also be used for the event of a

generator being out of service for maintenance or a breakdown.

Excess biogas is vented through a safety flame which indicates the presence of gas in the

system. It is proposed that the safety flame be adjusted manually to ensure that the consistent

and correct temperature is maintained when needed, in order to enhance anaerobic digestion

during colder conditions times. To speed up the digestion process and save costs on heating,

methane generated by the digester can be used to heat the mixture (Balsam 2006, Grelaud

2007, Lutge 2010, Tiepelt 2017).

Apart from electricity generation the gas can also be used to replace LPG usage in appliances

where the burner jets have been replaced by jets for natural gas jets in order to obtain the

same energy output (Steyn 2017). In the event of the gas being used directly for heating

applications, the electrical energy generation potential will have to be reviewed as the fuel

supply is now being divided between the two applications.

Output of the process (digestate as bio-fertiliser)

The anaerobic conditions in the digestion tank ensures the destruction of all major pathogens

such as E-coli, Salmonella and Campylobacter making the slurry safe for any form of

agricultural land application (Dennis and Burke 2001, Burton et al. 2009, Bond and

Templeton 2011, Msibi 2015, SAGEN and SABIA 2016). The fermented biomass discharge

(digestate) from the digester tank is in the form of a liquid mixture of dissolved and spent

organic matter. The digestate passes through a separating process where it is then separated in

solid bio-fertiliser matter (30 % to 35 % dry matter and liquid bio-fertiliser (1 % to 2 % dry

matter). The thin mud-like slurry is pumped into a lagoon storage unit and can be applied

onto farmland through an application system as a faded bio-fertiliser (Steyn 2017). The same

quantity of material that is fed into the digester is also taken out of the tank at the same

frequency as the loading rate. Chicken manure, fruit and vegetable discharge from the

digester can immediately be pumped to the irrigation system or it can be stored in the pond

for later distribution (Steyn 2017). The discharged from cow slurry is cooled in a one-day

holding pond before it is distributed for land application on a daily basis (Steyn 2017).


189

Maintenance

The estimated plant life and discount period for on-farm CSTR digester designs is

approximately 20 years. The mixer in the mixing pond as well as the slurry pump will require

major maintenance or replacement after five years of operation. Maintenance on rotating

machinery is required on years 5, 10, 15 and 20. Expected maintenance expenses are

approximately 1 % every year and 6 % every five years respectively of the total plant cost

(Steyn 2017). Generator maintenance interval should occur every 400/2000/8000 hours for

general/medium/major services with expected life of 40 000 hours, i.e. 10 years for 12h/day

operation. Re-conditioning overhaul is required on 40 000 hours (Steyn 2017).

On the gas handling system all the H2S condensate traps should be checked and drained on a

weekly basis. A total of 300 hours per year of generator down-time is required for routine

maintenance of the generator engine. During the generator servicing/maintenance, the plant

does not produce electricity except if the plant was constructed with generators in parallel

configuration, but the digester continues to produce methane gas that can be flared off (Steyn

2017).

Development procedure

Before any biogas digester of any scale is constructed in South Africa, it is recommended that

role definitions are identified and clarified before the project is underway (GreenCape

2017a). Table 1 illustrates the specific roles applicable in the process of the anaerobic value

chain as guideline to construction. The phases (pre-development, development, construction

and commissioning, operations and maintenance) are identified as being most relevant to the

South African biogas industry (AltGen, GIZ, SAGEN and GreenCape 2014). For the purpose

of biogas generation, pre-development and development are two separate phases; however,

going forward in South Africa, these two phases should be combined under “development”.

The regular monitoring of a biogas plant where processes are evaluated to identify

shortcomings and good performances as well as optimisation possibilities, is seen as the best

way to towards sustainable biogas production. Awareness of each stage of the process and the

possibilities for improvement is one of the most important steps towards optimal biogas

production (Bachman 2015, Steyn 2017).


190

Table 1: The specific roles applicable in the process of the anaerobic value chain, with

specific reference to the South African biogas industry (Source: AltGen, GIZ, SAGEN and

GreenCape 2014).

Pre-development Development Construction and

commissioning

Operations and

maintenance

Site selection,

Feedstock

evaluation,

Pre-environmental

assessment,

Preliminary plant

design,

Financial

prefeasibility

Project management,

Technical finalisation,

Environmental impact

assessment,

Permitting and

licensing,

Bankability and project

finance, Financial cost

analyses

Procurement,

Site and construction

management,

Commissioning,

Performance testing

Operations

management,

Technical maintenance

and monitoring,

Feedstock supply and

management,

Output management

(digestate),

Trouble shooting

It is further important to remain attentive to the strengths and mistakes of other projects and

to investigate new opportunities and possibilities for synergies. This process is continuous

and requires committed, innovative and dynamic operational managers that are motivated to

keep up with best practice and the latest technological developments (Bachman 2015, Steyn

2017).


191

APPENDIX H: Abbreviations

ABC - American Biogas Council

AD - Anaerobic digestion

AGET – African Green Energy Solutions

ASBR – Anaerobic Sequencing Batch Reactor

BD – Biogas Digster

BGK - Bundesgütegemeinschaft Kompost e.V. (Federal Association of Compost e.V.)

BMW - Bayerische Motoren Werke

BRICS – Brazil, Russia, India, China, South Africa

BSI PAS – British Standards Institution Publically Available Specification

CAGR - Compound Annual Growth Rate

CDM – Clean Development Mechanism

CEA – Clean Energy Africa

CER – Certified Emissions Reduction

CEPa – Combined Economic Potential

CEPb – Combined Environmental Potential

CFST – Continuous-flow Stirred Tank

CHP - Combined Heat and Power

CMF – Completely Mixed Flow Reactor

CPUT - Cape Peninsula University of Technology, South Africa

CSP – Combined Social Potential

CSTR – Continuously Stirred Tank Reactor

DA –Department of Agriculture

DAFF – Department of Agriculture, Fisheries and Forestry

DALY - Disability-Adjusted Life Years


192

DBSA - Development Bank South Africa

DEA – Department of Environmental Affair

DEA&DP – Environmental Affairs and Development Planning

DEDAT – Department of Economic Development and Tourism

DH – Department of Health

DIY – Do It Yourself

DM – Dry Matter

DNT – Department of National Treasury

DoE - Department of Energy

DTI - Department of Trade and Industry

DST - Department of Science and technology

EBA – European Biogas Association

EEG - Renewable Energy Sources Act, Germany

EIA - Environmental Impact Assessment

EPI – Environmental Performance Index

ESI-AFRICA - Electricity Supply Industry, AFRICA

ESI – Environmental Sustainability Index

ESKOM - state-owned vertically-integrated electricity company

EU – European Union

FAO - Food and Agriculture Organization of the United Nations

FERTASA – Fertiliser Society of South Africa

FEW - Food Energy Water

FS – Free State (South African province)

GBA – German Biogas Association

GDP – Gross Domestic Product

GEEF - Green Energy Efficiency Fund


http://www.fao.org/home/en/

193

GHG - Greenhouse Gas

GIZ - Deutsche Gesellschaft für Internationale Zusammenarbeit (German Society for

International Cooperation)

GPAER - Green Peace Advanced Energy Revolution

HRT – Hydraulic Retention Time

IBR – Induced Blanket Reactor

IDC - Industrial Development Corporation

IDM - Eskom Industrial Demand Side Management

IDM- Eskom Integrated Demand Management

IPPs - Independent Power Producers

IRP - Integrated Resource Plan for electricity

ISSF - International Stainless Steel Forum

KZN – Kwa-Zulu Natal (South Africa province)

LFG – Landfill Gas

LGM – Long Gap Mill

LPG – Liquefied Petroleum Gas

Ltd - Limited

MCEP - Manufacturing Competitiveness Enhancement Programme

MDGs - Millennium Development Goals

MFMA - Municipal Finance Management Act

MSA - Municipal Systems Act

MSW - Municipal Solid Waste

NDP - National Development Plan

NEM:WA – National Environmental Waste Act

NEMA - National Environmental Management Act

NEPAD - New Partnership for Africa’s Development


194

NERSA - National Regulator of South Africa

NEW – Nutrient, Energy and Water

NFSD - National Framework for Sustainable Development

NGO - Non-Governmental Organization

NNFCC - The National Non-Food Crops Centre

NSSD - The National Strategy for Sustainable Development and Action Plan

NT – National Treasury of South Africa

NT-MFMA - National Treasury of South Africa Municipal Financing Management Act

NWMS - National Waste Management Strategy

OECD - Organisation for Economic Co-operation and Development

OM – Organic Matter

Pty – Proprietary Company (business structure under Australian and South African Law)

REIPPPP - Renewable Energy Independent Power Producer Procurement Programme

RES - Retail Electricity Suppliers

RSA – Republic of South Africa

SA – South Africa

SAAEA - South African Alternative Energy Association

SAB – South African Brewery

SABIA – Southern Africa Biogas Industry Association

SADC - Southern African Development Community

SADEC - Socioeconomic data and application centre

SAGEN - South African-German Energy Programme

SALGA – South African Local Government Association

SAPA – South African Poultry Association

SAIREC – South African International Renewable Energy Conference

SANEDI - South African National Energy Development Institute


https://www.google.co.za/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&cad=rja&uact=8&ved=0ahUKEwj29dmxsbrUAhVBIcAKHeigBJYQFghBMAg&url=https%3A%2F%2Fnationalgovernment.co.za%2Funits%2Fview%2F284%2FEconomic-Infrastructure-Development%2FSouth-African-National-Energy-Development-Institute-SANEDI&usg=AFQjCNHpbwXc2EUbpKgcIKaekwxv6jymPA&sig2=3fTyQk9UFTwXECY1_hRBwg

195

SAOGA – South African Oil and Gas Alliance

SARETEC - The South African Renewable Energy Technology Centre

SC – Sustainability Category

SCF – Sustainability Category Factor

SDG – Sustainable Development Goals

SEPA - Scottish Environment Protection Agency

Sci. Tech. Co. Ltd - Science and Technology Company Limited.

SIR - Substrate Induced Respiration

SOM - Soil Organic Matter

SOP - Standard Offer Programme

SPC – Sustainability Potential Category

SPS - Sustainability Potential Score

SPSC – Sustainability Potential Score Category

SRT – Solid Retention Time

SSEG – Small-Scale Embedded generation

STATSSA – Statistics South Africa

S1 – Survey 1 (Farmers without biogas digesters)

S2 – Survey 2 (Farmers with biogas digesters)

TSPP – Total Sustainability Potential Percentage

TSPV – Total Sustainability Potential Value

UASB - Up-flow Sludge Blanket Digester

UFH – University of Fort Hare, South Africa

UN – United Nations

UNDP – United Nations Development Programme

UNEP – United Nations Environmental Programme

USAB – Upflow Anaerobic Sludge Blanket


196

USD - United states of America Dollar

USDA – United States Department of Agriculture

WC – Western Cape (South African Province)

WISA – Water Institute of Southern Africa

WISP – Western Cape Industrial Symbiosis Programme

WMFP- Waste Management Flagship Programme

WRC – Water Research Commission

WWF - World Wide Fund for Nature

WWF_ FEW - World Wide Fund for Nature Food Energy Water report

WWTW - Wastewater Treatment Works

ZAR – South African Rand


Documents

EVALUATING THE SUSTAINABLE POTENTIAL OF BIOGAS